Keywords

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Taxonomy: Historical and Current

Short Description of the Family

Pep.to.strep.to.coc.ca’ce.ae. N.L. n. Peptostreptococcus a bacterial genus, the type genus of the family; -aceae ending to denote a family; N.L. fem. pl. n. Peptostreptococcaceae the family of Peptostreptococcus (from Bergey’s Manual). The emendation of the original description (Ezaki 2009a) is given bellow.

Phylogenetically a member of the order Clostridiales (Prévot 1953), phylum Firmicutes. The family contains the type genus Peptostreptococcus, and genera Acetoanaerobium, Filifactor, Proteocatella, Sporacetigenium, and Tepidibacter (see comment below). Morphology of the cells varies from cocci to rods and filaments. Motile by means of peritrichous flagella or nonmotile. Some species form round or ovoid subterminal or terminal endospores. Anaerobic. Fermentative type of metabolism. Utilize proteinаceous substrates and carbohydrates; some species are asaccharolytic. Some species grow on amino acids using Stickland reactions. Catalase-negative or occasionally weakly positive. Mesophilic, moderately thermophilic or phychrotolerant. Neutrophilic. G+C values of DNA range between 24 and 54 mol%. Isolated from human and animal clinical samples, soil, sediments, manure, anaerobic sludge, and deep-sea hydrothermal vents.

Comment: At the time of the original description (Ezaki 2009a) the family contained the type genus Peptostreptococcus (Kluyver and van Neil 1936; emended by Ezaki et al. 2001), Filifactor (Collins et al. 1994), and Tepidibacter (Slobodkin et al. 2003; emended by Tan et al. 2012). Since then, ribosomal RNA sequence databases, SILVA (Pruesse et al. 2007; http://www.arb-silva.de), Ribosomal Database Project II (Cole et al. 2009; http://rdp.cme.msu.edu), and EzTaxon-e (Kim et al. 2012; http://eztaxon-e.ezbiocloud.net) classified three other genera—Acetoanaerobium (Sleat et al. 1985), Sporacetigenium (Chen et al. 2006), and Proteocatella (Pikuta et al. 2009) as members of Peptostreptococcaceae. These databases also include to Peptostreptococcaceae several validly published Clostridium and Eubacterium species: Clostridium bartlettii, C. bifermentans, C. difficile, C. ghoni, C. glycolicum, C. hiranonis, C. irregulare, C. litorale, C. lituseburense, C. mangenotii, C. mayombei, C. paradoxum, C. sordellii, C. thermoalcaliphilum and Eubacterium acidaminophilum, E. tenue, and E. yurii. Inclusion of these microorganisms to Peptostreptococcaceae was also proposed by Ludwig et al. 2009. Abovementioned species of Clostridium and Eubacterium need taxonomic revision and will not be covered in this chapter.

Phylogenetic Structure of the Family and Its Genera

Peptostreptococcaceae forms separate, well-defined clade in the order Clostridiales. The closest phylogenetic neighbors are genera Alkaliphilus, Natronincola, and Tindallia belonging to “Clostridiaceae 2” (LTP nomenclature; http://www.arb-silva.de) (Fig. 24.1). Within the family the genera Acetoanaerobium, Filifactor, and Proteocatella (and Eubacterium yurii) form deeply branching cluster; another cluster embrace the genera Peptostreptococcus, Sporacetigenium, and Tepidibacter (and 14 misclassified Clostridium species together with Eubacterium acidaminophilum and Eubacterium tenue). The genus Filifactor is most distantly related to other members of the family (83–87 % 16S rRNA gene sequence similarity).

Fig. 24.1
figure 1figure 1

Dendrogram showing the phylogenetic structure of the family Peptostreptococcaceae and the closest phylogenetic neighbors

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Molecular Analyses

DNA–DNA Hybridization Studies

DNA–DNA hybridization studies between different species of the family were performed only for two species of the genus Peptostreptococcus. Hybridization between P. anaerobius NCTC 11460T and P. stomatis strains W2278T and W3855 was 8 % and 14 %, respectively (Downes and Wade 2006). Intraspecies DNA–DNA hybridization between 8 strains of Filifactor alocis isolated from cats and the type strain of F. alocis ATCC 35896T isolated from human oral samples was in the range of 77–100 % (Love et al. 1987). For all others members of the family DNA–DNA hybridization studies were not carried out due to low values of 16S rRNA gene sequence similarity between the species (P. russellii and other species of Peptostreptococcus—93–96 %, Filifactor species—93 %, Tepidibacter species—94–95 %). Genera Acetoanaerobium, Proteocatella, and Sporacetigenium are represented by one species each.

Genome Comparison

The complete genomes of three species of Peptostreptococcaceae have been sequenced as the reference genomes for the Human Microbiome Project (Human Microbiome Jumpstart Reference Strains Consortium et al. 2010). The genome of Peptostreptococcus anaerobius 653-L (not a type strain of the species) (GenBank: ADJN00000000.1) has a size of 2.08 Mb, contains 1,930 genes (1,871 protein-coding genes), and its G+C content of DNA is 35.9 mol%. Peptostreptococcus stomatis DSM 17687. .GenBank: ADGQ00000000.1) has the genome size of 1.99 Mb with 1,659 genes, (1,600 protein-coding genes). The genome of Filifactor alocis ATCC 35896T (GenBank: CP002390.1) has a size of 1.93 Mb, contains 1,709 genes (1,641 protein-coding genes), and the mol% G+C of DNA is 35.4 %.

Phenotypic Analyses

The family Peptostreptococcaceae is morphologically diverse and includes cocci, rods, or long filaments. Most strains have the diameter of the cells in the range of 0.6–0.9 μm, irrespective of the cell shape. The family contains spore-forming as well as non-spore-forming species. Most species are Gram-stain-positive. The majority of the strains are obligately anaerobic chemo-organotrophs. The key metabolic property for all members of the family is anaerobic growth via fermentation of proteinаceous substrates and some carbohydrates. Peptostreptococcaceae includes mesophilic, psychrotolerant, and moderate thermophilc species. All strains grow at pH close to 7.0. The main morphological and chemotaxonomic characteristics of genera of Peptostreptococcaceae are listed in Table 24.1.

Table 24.1 Morphological and chemotaxonomic characteristics of genera of Peptostreptococcaceae
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Peptostreptococcus Kluyver and van Niel 1936, emend. Ezaki, Kawamura, Li, Li, Zhao and Shu 2001

Pep.to.strep.to.co’ccus. Gr. adj. peptos cooked, digested; N.L. masc. n. Streptococcus a bacterial genus name; N.L. masc. n. Peptostreptococcus the digesting streptococcus.

Cells of all three species of Peptostreptococcus are non-spore-forming Gram-stain-positive cocci, 0.8–1.0 μm in diameter. Cells may occur in pairs, irregular masses, or chains. Colonies of P. anaerobius are convex, 2.2–4.0 mm in diameter. Colonies of P. russellii are 2.0–3.0 mm in diameter, convex, opaque, smooth, and whitish in color. P. stomatis forms circular, high convex to pyramidal, opaque, shiny, and cream to off-white in color colonies, 0.8–1.8 mm in diameter, with a narrow, gray, peripheral outer ring. Optimal cultivation temperature for all species is 37 °C (Downes and Wade 2006; Ezaki 2009b; Whitehead et al. 2011). Members of Peptostreptococcus are obligately anaerobic chemo-organotrophs and metabolize peptone and amino acids to acetic, butyric, isobutyric, caproic, and isocaproic acid (Holdeman Moore et al. 1986; Ezaki et al. 2006). Carbohydrates are weakly fermented by all strains (Table 24.2). Urea is not hydrolyzed and indole is not produced by all species. P. russellii produces prodigious amounts of ammonia (>40 mM) from various nitrogen sources (Tryptone and Casamino acids) (Whitehead et al. 2011). Diamino acid of peptidoglycan is lysine (Ezaki 2009b). Comparison of other selected characteristics of species of the genus Peptostreptococcus is given in Table 24.2.

Table 24.2 Comparison of selected characteristics of species of the genus Peptostreptococcus
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Acetoanaerobium Sleat, Mah and Robinson 1985

A.ce.to.an.ae. ro’bi.um. L. n. acetum vinegar; Gr. pref. an not; Gr. n. aer air; Gr. n. bios life; M. L. neut. n. Acetoanaerobium vinegar anaerobe

The genus Acetoanaerobium includes so far only one species A. noterae—represented by one strain NOT-3T (= ATCC 35199T). Cell of A. noterae are straight rods, 0.8-μm wide and 1.0–5.0-μm long, motile with three or four peritrichous flagella. Cells stain gram-negative; the cell wall is atypical and is composed of two distinct layers, a darker inner layer and lighter outer layer. Colonies are rhizoid, opaque, and granular. Young colonies are white, but older colonies are brownish and up to 2 cm in diameter after 1 month of incubation. Obligately anaerobic. Yeast extract, maltose, and glucose are used for heterotrophic growth. Vitamins are not required. Compounds not supporting growth include arabinose, rhamnose, ribose, xylose, fructose, galactose, cellobiose, lactose, mannose, sucrose, melezitose, trehalose, erythritol, adonitol, arabitol, dulcitol, inositol, mannitol, sorbitol, formate, acetate, pyruvate, lactate, malate, fumarate, succinate, citrate, glutamate, methylamine, trimethylamine, and methanol. The strain produces acetate, propionate, iso-butyrate, butyrate, and iso-valerate (and little or no H2) during growth on yeast extract alone. When either glucose or maltose serves as a substrate, acetate is the only fermentation product. The main physiological feature that distinguishes Acetoanaerobium from other Peptostreptococcaceae is its capacity for lithotrophic acetogenic growth with H2:CO2. Yeast extract is required for growth and H2 utilization. Growth on yeast extract and H2:CO2 is biphasic, with an initial rapid growth phase independent of the presence of H2. This is followed by H2-dependent acetate production during the second slower growth phase (Sleat et al. 1985). Temperature and pH ranges and optima for growth and G+C content of DNA are presented in Table 24.1.

Filifactor Collins, Lawson, Willems, Cordoba, Fernández-Garayzábal, Garcia, Cai, Hippe and Farrow 1994

Fi.li.fac’tor. L. n. filum thread; L. masc. n. factor maker; N.L. masc. n. Filifactor thread-maker.

Cells of Filifactor are rods 0.4–0.7 μm in diameter and 1.5–7.0 μm in length with rounded to tapered ends that occur singly, in pairs, and occasionally in chains or filaments. F. villosus can form filaments up to 30 μm in length. Cells of F. villosus have variable Gram-staining properties—positive in young (24–48 h) cultures and negative in old (7 d) cultures. However, thin-section electron microscopy studies have shown that the structure of the cell wall and the mode of the division are consistent with the Gram-positive bacteria. Cells of F. alocis stain Gram-negative. Cells of both Filifactor species are nonmotile and do not have flagella, but some of the strains have been shown to have twitching or end-over-end type of motility. F. villosus forms oval subterminal endospores that caused a slight distention of the sporangium. Formation of endospores by F. alocis was not observed. Colonies of Filifactor are small (0.5–1.0 mm) and nonhemolytic. Members of Filifactor are obligately anaerobic chemo-organotrophs. All strains produce acetate, butyrate, and H2 as fermentation products (Table 24.3). Both Filifactor species do not utilize sugars; no acid is produced from esculin, fructose, glucose, maltose, mannitol, mannose, melibiose, ribose, sucrose, or xylose. Threonine and lactate are not utilized. Nitrate is not reduced. Indole, lecithinase and lipase are not produced. Esculin is not hydrolyzed. Milk and meat are not digested (Love et al. 1979; Cato et al. 1985, 1986; Jalava and Eerola 2009). Peptidoglycan (position 3, bridge) is Orn, d-Asp (Ezaki 2009a). Comparison of other selected characteristics of species of the genus Filifactor is given in Table 24.3.

Table 24.3 Comparison of selected characteristics of species of the genus Filifactor
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Proteocatella Pikuta, Hoover, Marsic, Whitman, Lupa, Tang, and Krader 2009

Pro.te.o.ca.tel’la. N.L. n. proteinum protein; N.L. pref. proteo- prefix referring to protein used in compound words; L. fem. n. catella small chain; N.L. fem. n. Proteocatella a small chain using proteins.

The genus Proteocatella includes so far only one species, P. sphenisci, represented by one strain PPP2T (=ATCC BAA-755T). Cells of P. sphenisci are flexible, motile rods, 0.7–0.8 × 3.0–5.0 μm, that tend to form long chains. Multiplies by fission, sometimes unequally with the formation of terminally round mini-cells. Motile by means of flagella. Forms spherical endospores in non-swollen sporangia. Cell wall has Gram-positive structure. Colonies are creamy yellow and rounded lens-shaped with a diameter of 1–2 mm. Obligate anaerobe with fermentative type of metabolism. Catalase-negative. Grows with peptone, bacto-tryptone, Casamino acids, oxalate, starch, chitin, and yeast extract. The strain grows on sodium oxalate only in medium supplemented with selenium as a trace element; cell morphology on this substrate was atypical, with a tendency for the cells to appear swollen and with a hexagonal crystalline shape. No growth is observed on formate, acetate, lactate, pyruvate, propionate, butyrate, citrate, methanol, ethanol, glycerol, acetone, d-mannitol, d-glucose, d-fructose, d-ribose, trehalose, d-arabinose, maltose, d-mannose, lactose, sucrose, cellobiose, pectin, N-acetylglucosamine, urea, trimethylamine, triethylamine, or betaine. Separate amino acids on mineral medium supplemented with yeast extract (0.1 g/l) do not support growth. The Stickland reaction is negative. End products of peptone fermentation are acetate, butyrate, ethanol, and minor amounts of hydrogen and carbon dioxide. NaCl range for growth is 0–4 % (w/v); optimal growth at 0.5 % (w/v) NaCl. Alkalitolerant, psychrotolerant mesophile (Pikuta et al. 2009). Temperature and pH ranges and optima for growth, major cellular fatty acids and G+C content of DNA are presented in Table 24.1.

Sporacetigenium Chen, Song and Dong 2006

Spo.ra.ce.ti.ge’ni.um. Gr. n. spora seed; L. n. acetum vinegar; Gr. v. gennao to produce; N.L. neut. n. Sporacetigenium spored vinegar (acetate) producer.

The genus Sporacetigenium includes so far only one species, S. mesophilum, represented by two strains. The physiological characteristics of the type strain ZLJ115T (=DSM 16796T) are described below. Cells of S. mesophilum are rods 0.9–1.0 × 3.6–7.3 μm in size, occurring singly or in short chains and motile by peritrichous flagella. The cells have Gram-positive wall structure; the peptidoglycan of the cell wall contains meso-DAP. Ovoid endospores are formed in the ends of cells, resulting in swollen cells. Colonies on PYG agar are milk white, smooth, circular, entire and translucent, slightly convex, and reaches 1 mm in diameter after cultivation at 37 °C for 48 h. Obligately anaerobic and chemo-organotrophic. Oxidase and catalase are not produced. Acid is produced from d-glucose, d-fructose, l-arabinose, d-xylose, and d-maltose. d-Galactose, d-mannose, cellobiose, sucrose, rhamnose, trehalose, melibiose, melezitose, and raffinose are fermented weakly. Acid is not produced from sorbose, starch, inulin, glycogen, salicin, amygdalin, glycerol, adonitol, dulcitol, erythritol, inositol, mannitol, or sorbitol. Fermentation of d-lactose and ribose is variable. The following compounds are not utilized: methanol, ethanol, 1-propanol, citrate, fumarate, malate, succinate, malonic acid, hippurate, sodium gluconate, butanedioic acid, b-hydroxybutyric acid, phenylacetic acid, cellulose, and xylan. The major fermentation products from glucose are acetate, ethanol, hydrogen, and carbon dioxide. Peptone may serve as nitrogen source. Starch and aesculin are hydrolyzed, whereas gelatin is not. Milk is not curdled. Urease, lecithinase, and lipase are not produced. Methyl red test is positive while Voges–Proskauer test is negative. Nitrate, sulfate, and sulfur are not reduced. H2S and NH3 are produced from PYG. The strain could grow in the presence of 0–4 % (w/v) NaCl (Chen et al. 2006). Temperature and pH ranges and optima for growth, major cellular fatty acids and G+C content of DNA are presented in Table 24.1.

Tepidibacter Slobodkin, Tourova, Kostrikina, Chernyh, Bonch-Osmolovskaya, Jeanthon and Jones 2003, emend. Tan, Wu, Zhang, Wu and Zhu 2012

Te.pi.di.bac’ter. L. adj. tepidus warm; N.L. bacter masc. equivalent of Gr. neut. dim. n. bakterion rod; N.L. masc. n. Tepidibacter a warm rod.

Cells of Tepidibacter are straight to slightly curved rods 0.7–1.6 μm in diameter and 2.3–6.0 μm in length occurring singly, in pairs, or in short chains. Cells exhibit tumbling motility due to peritrichous flagellation. All three species of Tepidibacter have Gram-positive type cell wall and form round or ovoid refractile terminal or subterminal endospores. In the late-exponential phase of growth, up to 30 % of the cells of T. thalassicus contain spores. All Tepidibacter species form colonies in anaerobic agar. T. thalassicus and T. formicigenes are moderate thermophiles with temperature range for growth 30–60 °C; T. mesophilus is a mesophile with upper temperature limit of 40 °C. T. thalassicus and T. formicigenes grow at marine salinity; T. mesophilus shows the best growth with 0.5–1.0 % of NaCl but can tolerate up to 9 % of NaCl or sea salts. Members of Tepidibacter are anaerobic or aerotolerant (T. mesophilus) chemo-organotrophs. They ferment a number of proteinaceous substrates and carbohydrates and are able to perform the Stickland reaction. The best growth of T. thalassicus can be obtained on complex proteinaceous substrates such as tryptone, casein, and peptone or on starch. Carbohydrates, in the presence of yeast extract, slightly stimulate growth of T. thalassicus. Growth of T. formicigenes and T. mesophilus on sugars is more efficient. Differences in substrates utilization by Tepidibacter species are shown in Table 24.4. T. thalassicus and T. mesophilus reduce elemental sulfur to hydrogen sulfide, but sulfur reduction does not stimulate growth. All strains of Tepidibacter do not use nitrate, nitrite, Fe(III), sulfate, sulfite, and thiosulfate as electron acceptors. Oxidase and catalase activities are negative for all strains. All Tepidibacter species produce ethanol and acetate from glucose; in addition T. thalassicus forms moderate amounts of H2 and CO2, and T. formicigenes produces formate as a main fermentation product (Slobodkin et al. 2003; Slobodkin 2009; Urios et al. 2004; Tan et al. 2012). The major cellular fatty acid in the three species of Tepidibacter is iso-C15: 0, it constitutes 97.0, 77.7, and 51.8 % of the total fatty acids in T. thalassicus, T. formicigenes, and T. mesophilus, respectively (Tan et al. 2012). Differentiating characteristics of species of the genus Tepidibacter is given in Table 24.4.

Table 24.4 Differentiating characteristics of the species of the genus Tepidibacter
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Isolation, Enrichment, and Maintenance Procedures

Members of the family Peptostreptococcaceae can be enriched and isolated at anaerobic conditions in media that are rich in proteinaceous substances. All species have complex growth requirements, which may include vitamins, cofactors, and amino acids.

Peptostreptococcus anaerobius and P. russellii grow well on anaerobic chopped meat medium (DSM medium 78; http://dsmz.de). P. stomatis strains can be cultivated on fastidious anaerobe agar supplemented with 5 % horse blood in the atmosphere of 80 % N2, 10 % H2, 10 %, CO2 or on anaerobic PYG medium supplemented with glucose (4.0 g/l), cellobiose (1.0 g/l), maltose (1.0 g/l), and soluble starch (1.0 g/l) (DSM medium 104 modified) (Downes and Wade 2006; Ezaki 2009b). Strain of P. stomatis was recovered from subgingival plaque using single-cell long-term cultivation method to minimize the effect of fast-growing microorganisms (Sizova et al. 2012). Colonies of P. russellii can be obtained on agar plates incubated in an anaerobic chamber in an atmosphere of CO2:H2 (96:4) on the medium containing buffer, salts, yeast extract (0.3 %), Bacto-Tryptone (1 %), and Casamino Acids (1 %) (Whitehead et al. 2011). All strains of Peptostreptococcus also grow on brain heart infusion medium under anaerobic conditions. In most cases, the temperature for enrichment, isolation, and cultivation of Peptostreptococcus species was 37 °C.

Acetoanaerobium noterae was isolated using anaerobic reduced mineral medium with H2:CO2 in the gas phase supplemented with 2.0 g/l of yeast extract. In the complete absence of yeast extract, H2 was not utilized; at least 0.5 g/l was required for sustainable growth. A. noterae can also be cultivated without molecular hydrogen, on yeast extract (2.0 g/l) alone, or on maltose or glucose in the presence of 0.5 g/l of yeast extract. Vitamins are not required for the growth of this microorganism (Sleat et al. 1985).

Filifactor villosus can be isolated and grown on sheep blood agar plates and brain heart infusion agar plates incubated anaerobically. Cooked meat plus peptic digest of meat broth alone or supplemented with 0.4 % glucose, 0.1 % cellobiose, 0.1 % maltose, and 0.1 % starch can be used for cultivation of pure cultures (Love et al. 1979). Cultures of this microorganism can also be maintained on anaerobic chopped meat medium or chopped meat medium with carbohydrates (DSM medium 78 and DSM medium 110; http://dsmz.de). Fastidious anaerobic agar plates with and without 7 % (w/v) bovine blood have been used for cultivation of pure cultures of F. alocis under anaerobic conditions (Jalava and Eerola 1999).

Proteocatella sphenisci was enriched and isolated in a pure culture at the temperature +2 °C. Anaerobic mineral medium used for isolation included peptone (3 g/l) and yeast extract (0.2 g/l). Initial salinity of enrichments was 30 g/l of NaCl; however, the optimal NaCl concentration for pure culture of P. sphenisci was 5 g/l (Pikuta et al. 2009).

Strains of Sporacetigenium mesophilum were isolated and routinely cultivated in pre-reduced peptone/yeast extract/glucose medium (Chen et al. 2006). Type strain could be maintained in DSM medium 104b (PYX-medium, http://dsmz.de).

Thermophilic Tepidibacter species can be enriched in the temperature range of 45–55 °C in anaerobic medium of marine salinity supplemented with proteinaceous substrates (Slobodkin et al. 2003; Urios et al. 2004). T. thalassicus, T. formicigenes, and T. mesophilus were isolated in the presence of 0.2–1.0 g/l of yeast extract with casein (10 g/l), peptone (0.5 g/l), or Casamino acids (3 g/l) as a main carbon source, respectively. T. thalassicus rapidly hydrolyzes casein (Hammerstein grade) that results in visual disappearance of the casein flocks and may help in the detection of growth. All Tepidibacter strains form colonies in 1.5 % (w/v) anaerobic agar, and Hungate roll tube or agar block techniques can be used for the isolation of a single colony (Hungate 1969). Members of the genus Tepidibacter may be maintained on the medium of Slobodkin et al. (2003) with peptone or casein as a substrate or on the glucose/yeast extract/peptone medium of Urios et al. (2004). All three species of Tepidibacter show a good growth on DSM medium 985 with 1 % peptone (Tan et al. 2012; http://dsmz.de). Reproducible growth of T. thalassicus and T. mesophilus can be obtained in liquid anaerobic medium lacking sulfide as a reducing agent (Slobodkin et al. 2003; Tan et al. 2012). Freeze-drying of the cultures results in good recovery. T. mesophilus may be preserved in 25 % glycerol at −80 °C. Liquid cultures of T. thalassicus may be stored at +4 °C for 10–12 months without loss of viability.

Ecology

Members of the family Peptostreptococcaceae were isolated from various environments including clinical human and animal samples, manure, soil, marine and terrestrial sediments, and deep-sea hydrothermal vents.

Peptostreptococcus species have been found in body and feces of humans and vertebrates. Taking into consideration that the group of the anaerobic Gram-positive cocci was subjected to major revision (Ezaki et al. 2006), it is difficult to determine the exact taxonomic status of the strains referred as the members of the genus Peptostreptococcus in reports dated before 1990s because of the absence of 16S rRNA gene sequence data. Numerous studies point to the presence of Peptostreptococcus strains in human oral cavity—P. anaerobius is a component of the human oral microbiome (Chen et al. 2010; http://www.homd.org); eight strains of P. stomatis, including the type strain, have been isolated from oral cavity (Downes and Wade 2006). Different phylotypes of Peptostreptococcaceae related to Peptostreptococcus species have been detected in oral samples by culture-independent methods (Paster et al. 2001; Munson et al. 2002; Sakamoto et al. 2004; Dewhirst et al. 2010). Strains of P. anaerobius have been isolated also from various human non-oral infection and abscesses and from intestine, vagina, and skin of healthy individuals (Downes and Wade 2006; Ezaki 2009b; Human Microbiome Jumpstart Reference Strains Consortium et al. 2010). Besides the human body, species of the genus Peptostreptococcus have been found in other vertebrate hosts. The presence of Peptostreptococcus spp. in canine oral cavity has been proven by culture-dependent and culture-independent techniques (Elliott et al. 2005; Dewhirst et al. 2012). Peptostreptococcus strains have been isolated from the rumen of dairy cows, deer, and sheep (Russell et al. 1988; Paster et al. 1993; Attwood et al. 1998). Most probably in the rumen ecosystem, Peptostreptococcus spp., that produce very high concentration of ammonia, but are not able to hydrolyze intact proteins and do not use carbohydrates, occupy a niche of peptide- and amino acid-degrading microorganism and depend on proteolytic bacteria (Attwood et al. 1998). One isolate of Peptostreptococcus has been obtained from feces of the mallard duck (Murphy et al. 2005). Seven strains of P. russellii have been isolated from a swine manure storage pit located near Peoria, IL, USA. In this habitat, concentration of the cells of P. russellii was at least 108 cells per ml and constituted approximately 0.1–1 % of the culturable bacterial population present in the swine manure samples (Whitehead et al. 2011).

The type strain of Acetoanaerobium noterae has been isolated from sediment of the Notera 3 oil exploration drilling site in the Hula swamp area of Galilee, Israel. The most probable number analysis of the drilling site sample yielded 1.75 × 105 H2-oxidizing acetogens per gram (wet weight) (Sleat et al. 1985). Uncultured Acetoanaerobium clones (>98 % 16S rRNA gene sequence similarity with the type strain, sequence length >1,300 bp, retrieved from NCBI databases using BLAST, http://blast.ncbi.nlm.nih.gov) have been detected in production waters and sewage of oil reservoirs (accession numbers AY570564, DQ011249), wastewater treatment systems (FJ167476, AF234746, HE576030), and dechorinating microbial consortia (AJ488068, GQ377124).

Species of the genus Filifactor so far have been found only in human and animal samples. Eleven strains of F. villosus including the type strain have been isolated from subcutaneous abscesses of cats (Love et al. 1979). F. alocis is associated with oral cavity, and a large number of strains of this microorganism have been isolated from human gingival sulcus of patients with gingivitis or periodontitis, from oral cavities of cats, and from soft tissue infections of cats caused by contamination from oral cavities (Cato et al 1985; Love et al. 1987; Jalava and Eerola. 2009). Filifactor spp. are the components of the human and canine microbiomes where they have been detected by culture-independent methods (Dewhirst et al. 2010, 2012; Kong et al. 2012).

The type strain of Proteocatella sphenisci has been isolated from a sample of guano of the Magellanic penguin (Spheniscus magellanicus) in Chilean Patagonia. The physiological characteristics of P. sphenisci—tolerance to low temperature (down to 2 °C), high pH, and marine concentrations of NaCl—reflect the environmental conditions of the habitat. Magellanic penguins are endemic to the southern tip of South America, a region with a very cold climate. The ability of the strain to use exclusively products of proteolysis and oxalate (but not sugars) is probably due to the restricted diet of these penguins that feed on marine fish and crustaceans (Pikuta et al. 2009). Three different 16S rRNA gene sequences belonging to Proteocatella have been found in canine oral microbiome (Dewhirst et al. 2012) and human skin microbiome (GenBank accession number HM266866) (Kong et al. 2012). Other uncultured Proteocatella clones have been detected in various wastewater treatment systems (HM467987, FJ645707, CU925306), in river estuary of Northern Taiwan (DQ234248), and in a drinking water reservoir in Greece (GQ340217) (>98 % 16S rRNA gene sequence similarity with the type strain, sequence length >1,300 bp, retrieved from NCBI databases using BLAST, http://blast.ncbi.nlm.nih.gov).

Both strains of Sporacetigenium mesophilum have been isolated from the sludge of an anaerobic digester treating municipal solid waste and sewage in Zhangzhou city, Fujian province, PR China (Chen et al. 2006). Uncultured clones of Sporacetigenium (>98 % 16S rRNA gene sequence similarity with the type strain, sequence length >1,300 bp, retrieved from NCBI databases using BLAST) have been detected in such different habitats such as anaerobic zones of Tinto River (JQ815621), shallow-sea hydrothermal vent Tutum Bay, Papua New Guinea (JN881597), alkaline lake Alchichica, Mexico (JN825560), tallgrass prairie soil (EU134685), and rhizosphere of reed (AB240265).

Thermophilic strains of Tepidibacter inhabit deep-sea hydrothermal vents. The type strain of T. thalassicus has been isolated from the outer wall of a actively venting hydrothermal sulfidic chimney-like deposit (“black smoker”) covered with the polychetous annelid Alvinella spp. (13o N to the East-Pacific Rise, hydrothermal site Genesis, depth 2,650 m) (Slobodkin et al. 2003). Strain NS55-A that is closely phylogenetically related to T. thalassicus (16S rRNA gene sequence similarity—98.9 %) have been obtained from black exterior surface layer of hydrothermal chimney structure (North Big Chimney, Iheya North field in the Mid-Okinawa Trough, depth ca. 1,000 m) (Nakagawa et al. 2005). T. formicigenes has been isolated from hydrothermal fluid (the Menez-Gwen hydrothermal site, Mid-Atlantic Ridge, 37o 51′ N 31o 31′ W, depth 800–1,000 m) (Urios et al. 2004). Location of these vents, two of which are in different parts of Pacific Ocean and one is in Atlantic Ocean, suggests wide geographical distribution of Tepidibacter species in marine hydrothermal environments where they probably function as decomposers of organic matter produced by deep-sea biota. Tepidibacter spp. also inhabit terrestrial geothermal environments; T. formicigenes strain JB2 (99 % 16S rRNA gene sequence similarity with the type strain of T. formicigenes) has been obtained from Tunisian hot spring with salinity 1.8–2.0 % (Sayeh et al. 2010). Mesophilic representatives of the genus have been found in cold marine sediments and soils. Strain UXO3-5 (96.8–97.3 % 16S rRNA gene sequence similarity with T. thalassicus and T. formicigenes) has been isolated from marine sediments in unexploded ordnance disposal sites (800-m offshore Oahu Island, Hawaii, depth 10–21 m). This microorganism, obtained in pure culture under mesophilic conditions (21 °C), accounts for 4.5 % of total anaerobes in sediment (Zhao et al. 2007). T. mesophilus has been isolated from the completely different habitat—the soil polluted by crude oil (the Karamay Oil Field, 45o 36′ N 84o 57′ E, northwestern China). Ecological functions of T. mesophilus are currently unknown, but the aerotolerance of this strain suggests its adaptation to soil environments (Tan et al. 2012). Uncultured Tepidibacter clones (>95 % 16S rRNA gene sequence similarity with the type strains of T. thalassicus, T. formicigenes, and T. mesophilus, sequence length >1,300 bp, retrieved from NCBI databases using BLAST, http://blast.ncbi.nlm.nih.gov) have been detected in environmental samples and enrichment cultures obtained from cold and hydrothermal marine ecosystems: seaweed bed associated with marine hot springs on East Coast of Kalianda Island, Indonesia (accession number JQ670702); coastal soil of Gulf of Khambhat, India (JX240907); superficial sediments of Milazzo Harbor, Italy (AJ810557); and polluted coastal seawater in Tunisia (CU914830 to CU914837).

Pathogenicity: Clinical Relevance

Among the members of the family Peptostreptococcaceae pathogenicity are definitely shown only for the species of the genus Filifactor. Strains of this genus have been isolated from human gingival sulcus of patients with gingivitis or periodontitis, from oral cavities of cats, and from subcutaneous wound abscesses of cats; therefore, a pathogenic role of Filifactor in mixed anaerobic infections was suggested (Cato et al. 1985; Love et al. 1979, 1987). Association of F. alocis with periodontal diseases was also confirmed by culture-independent studies (Kumar et al. 2005; Siqueira and Rocas 2003). F. alocis is involved in the formation of periodontal biofilms in patients suffering from generalized aggressive periodontitis and chronic periodontitis and can be considered an excellent marker organism for periodontal disease. F. alocis predominantly colonized apical parts of the pocket in close proximity to the soft tissues and was involved in numerous structures that constitute characteristic architectural features of subgingival periodontal biofilms (Schlafer et al. 2010). F. alocis has virulence attributes that can enhance its persistence under oxidative stress conditions and mediate invasion of epithelial cells by Porphyromonas gingivalis (Aruni et al. 2011). Recently, the pathogenic mechanisms of F. alocis in periodontal diseases have been investigated. When infected with F. alocis, primary cultures of gingival epithelial cells (GECs) stimulate the secretion of the pro-inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α. F. alocis also induced apoptosis in GECs through pathways that involved caspase-3 but not caspase-9. Apoptosis was coincident with inhibition of mitogen-activated protein kinase kinase activation (Moffatt et al. 2011).

Pathogenicity of the members of the genus Peptostreptococcus currently is difficult to assess. In the Internet-available medical literature, there are about 2,000 references about involvement of Peptostreptococcus in clinical cases. However, in the majority of these studies, the data on 16S rRNA gene sequence are not provided, so it is impossible to determine if the authors are dealing with the species of the genus Peptostreptococcus sensu stricto or with the other Gram-positive anaerobic cocci. Information about clinical relevance and pathogenicity of Gram-positive anaerobic cocci before taxonomic revision of this group is summarized in review by Murdoch (1998). Representatives of the genus Peptostreptococcus are frequently isolated from clinical samples of healthy and sick individuals (see section “Ecology”). Strains of P. anaerobius have been isolated from leg ulcer, urinary tract infection, ankle wound, buttock abscess, and vaginal infection (Downes and Wade 2006). P. anaerobius can cause primary sternal osteomyelitis (Chen et al. 2012). Strains of P. stomatis have been isolated from dento-alveolar abscesses, endodontic infections, a periodontal pocket, and from a pericoronal infection (Downes and Wade 2006). Recent culture-independent studies show that acute noma disease (gangrenous disease that leads to severe disfigurement of the face) and necrotizing gingivitis are associated with large increase in counts of members of the Peptostreptococcus genus (Bolivar et al. 2012). On the other hand, species of Peptostreptococcus are a part of the normal oral and vaginal microflora (Zhou et al. 2004; Aas et al. 2005).

There are no reports on pathogenicity and medical relevance of the representatives of Acetoanaerobium, Proteocatella, Sporacetigenium, and Tepidibacter. No strains of these genera were found in clinical samples.

Antibiotic sensitivity of the members of genera Peptostreptococcus, Acetoanaerobium, Filifactor, and Proteocatella is shown in Table 24.5. Majority of the strains are susceptible to penicillin and chloramphenicol. It is worth to note that Proteocatella sphenisci is resistant to ampicillin, a characteristic that is rare in environmental bacterial strains.

Table 24.5 Antibiotic sensitivity of the members of the family Peptostreptococcaceae
Full size table

Application

To date, microorganisms belonging to Peptostreptococcaceae did not find any application in industrial or bioremediation processes; however, there are a number of reports about biotechnological potential of the members of the family.

Peptostreptococcus russellii may play a role in swine manure management. It produces prodigious amounts of ammonia (> 40 mM) from different nitrogen sources (Tryptone and Casamino acids) and belongs to the so-called hyper-ammonia-producing microorganisms. This group of organisms may be important in the digestion and fermentation of proteinaceous material in the manure and the production of ammonia and other compounds (Attwood et al. 1998; Whitehead and Cotta 2004). The fermentation of amino acids such as tryptophan, phenylalanine, and tyrosine may give rise to the production of indole and phenolic compounds (such as skatole), contributing to the foul odors associated with swine facilities (Whitehead et al. 2011).

Tepidibacter thalassicus has the potential for immobilization of radionuclides such as technetium(VII). Washed cell suspensions of T. thalassicus completely reduced technetium [99Tc(VII)], supplied as soluble pertechnetate with molecular hydrogen or peptone as an electron donor, forming highly insoluble Tc(IV)-containing grayish-black precipitate. This capacity can be used during bioremediation of thermally insulated contaminated environments and in biotechnological treatment of the heated nuclear waste streams (Chernyh et al. 2007). Under mesophilic conditions, Tepidibacter sp. strain UXO-3-5 can metabolize octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), a toxic explosive known to be resistant to biodegradation. This organism plays a significant role in HMX removing in sites of undersea deposition of unexploded ordnance in Hawaii (Zhao et al. 2007).

Production of acetate from molecular hydrogen by Acetoanaerobium noterae and formation of H2 during fermentation of glucose by Sporacetigenium mesophilum also deserve attention for biotechnological applications (Sleat et al. 1985; Chen et al. 2006).