1 Introduction

There is a necessity for adequate food requirements to overcome the increasing population demand at global level. To increase the productivity, farmers are using chemical-based fertilizers that are improving crop yield, however it is proven that application of these chemicals have adverse impact on soil productiveness (Yatoo et al. 2021; Fatima et al. 2021). A profitable mode of availing phosphorus to plants is using PSMs (Kirui et al. 2022). Efforts to enhance the soil biological system are essential to address the aforementioned issues. Although phosphorus (P) is a macronutrient, it is crucial for plant health and often required in significant amounts (Kirui et al. 2022; Rawat et al. 2021; Kalayu 2019), contributing to 0.2 percent dry weight of plant (Maharajan et al. 2018). It is one of the main components of phosphoplipids, phosphoproteins, and cofactors and is the constituent of skeletal structure of genetic material of living creatures (Ozane 1980; Bai et al. 2020; Timofeeva et al. 2022; Feng et al. 2024). P is the vital element associated in plant metabolism with many functions like cell division, nitrogen fixation, nucleic acid and protein formation, crop quality, disease resistance (Khan et al. 2014; Nesme et al. 2018; Koch et al. 2018). Though soil holds entire P in organic and inorganic form, maximum of them remains locked thus becomes unavailable to plants (Kalayu 2019; Dong et al. 2023).

Phosphorus deficiency distresses root architecture (Williamson et al. 2001). Phosphorus deficiency leads to pale, dull, blue-green leaves and delayed maturity (Bai et al. 2013). This macronutrient is utilized in an inorganic form either as H2PO44− or HPO42− or both (Hinsinger 2001; Divjot et al. 2021; Li et al. 2021). Numerous microorganisms produce low molecular weight organic acids, such as acetic acid, citric acid, oxalic acid, malic acid, and gluconic acid, which help solubilize P. These acids chelate cationic partners of phosphorus ions, thereby releasing phosphorus directly into the soil solution. Microorganisms, including various species of Aspergillus, Fusarium, Penicillium, Serratia, Bacillus, Azotobacter, Rhizobium and Pseudomonas, play a crucial role in this process. They assimilate phosphorus and prevent its immobilization or fixation, thus enhancing its availability to plants. This microbial activity is vital for maintaining soil fertility and promoting healthy plant growth (Khan et al. 2009a, b, c).

Microorganisms, through various processes such as mineralization, solubilization, and decomposition influences soil fertility. Microbes increase phosphorus availability by solubilizing the locked form of phosphorus (Chen et al. 2006; Kang et al. 2002). Microorganisms acts as a substitute for phosphorus fertilizers (Padmavathi and Usha 2012). From couple of decades numerous PSMs studies were under focus which include various species of Serratia, Micrococcus, Enterobacter, Azotobacter, Rhizobium and Micrococcus (Kirui et al. 2022; Chawngthu et al. 2020; Mohamed et al. 2018; Yadav et al. 2016) Rhizobium, Arthrobacter and Rahnella aquatilis HX2 (Chawngthu et al. 2020; Zhang et al. 2019; Liu et al. 2019), Leclercia adecarboxylata (Teng et al. 2019a), the other fungi function in same way which includes species of Penicillium, Aspergillus, Fusarium, and Hymenella (Zhu et al. 2011; Ichriani et al.2018) are potential PSMs and can be used as an substitute for phosphorus fertilizers (Padmavathi and Usha 2012). Phosphate solubilizing microbes produce some essential phyto hormones like cytokinins, auxins, and gibberellins which have a role in cell division, differentiation, root and shoot development, germination, flowering (Puri et al. 2020).

Moreover, bioremediation has attracted a lot of scientific attention in recent years. Heavy metals like Cu, Pb, Ni, Hg, Cd, and Zn among others, play a role in several environmental problems. Heavy metals pose a significant challenge as pollutants that are not easily broken down. These pollutants can originate from either natural sources or human activities (Tan et al. 2021). Microorganisms like bacteria, fungi, yeast and actinomycetes are known for bioremediation of heavy metals. Microbes have demonstrated remarkable effectiveness in the remediation of environmental pollutants (Ahmed et al. 2022; Hamid et al. 2023a; Hamid et al. 2023b). Various phosphate solubilizing microbial strains which belong to genus Bacillus, Pseudomonas, Paenibacillus, Staphylococcus, Aspergillus, Rhizopus, Trichoderma and Brevibacterium have been reported as bioremediators (Khambhaty et al. 2008; Vala and Sutariya 2012; Yahaghi et al. 2018; Bashir et al. 2018a, b).

2 Phosphorus Solubilizing Microorganisms (PSMs)

PSMs are abundant in the soil and may be readily isolated from a diverse rhizospheric soils (Manoj et al. 2018). The number of P solubilizers present in a soil are based on many factors like organic content and properties of soil (Menezes-Blackburn et al. 2013). Phosphorus solubilizers are observed in rhizosphere where many chemical reactions occur (Mitra et al. 2020; Chawngthu et al. 2020). PSMs play central part in phosphorus cycling in the environment (Khan et al. 2024; Mitra et al. 2020; Saha and Biswas 2009). Since 1903, the PSMs (bacteria, fungi, actinomycetes) that occurs naturally as per reports of Khan et al. (2009a, b, c) play an important role in phosphorus solubilization in soil.

Phosphorus occurs either in organic form or as phosphorite and many solubilizing microorganisms have been obtained and identified from varied habitats (Acevedo et al. 2014; Taktek et al. 2015; Bashir et al. 2018a; Chawngthu et al. 2020; Divjot et al. 2021). PSMs includes many species of Azotobacter, Bacillus, Serratia, Enterobacter, Micrococcus, Rhizobium, Penicillium, Aspergillus, Rhizopus, Fusarium etc. (Kour et al. 2020). These microbial species have been isolated and screened from aquatic and terrestrial habitats (De Souza et al. 2000; Chakdar et al. 2018). These were also isolated and identified from rhizosphere of rice, banana, vegetable, apple, pear, walnut (Chawngthu et al. 2020; Bashir et al. 2019a, b; Bashir et al. 2017, 2018a, b; Kumar et al. 2013; Naik et al. 2008). A part from many species of Bacillus and Pseudomonas other potential P-solubilizers are Rhodococcus, Serratia, Arthrobacter, Chryseobacterium, Xanthomonas, Azotobacter, Klebsiella, Enterobacter, Acinetobacter (Wani et al. 2007; Kumar et al. 2013; Chen and Liu 2019; Chawngthu et al. 2020; Zhao et al. 2023). Here are some examples of PSMs that have been studied (Table 1).

Table 1 Phosphorus solubilizing microorganisms and their sources of isolation
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Among all PSMs in soil PSB constitutes 1 to 50%, fungi constitute 0.1 to 0.5% (Chen et al. 2006). Among actinomycetes, 20% of the genera Micromonospora, Actinomyces, and Streptomyces can solubilize P (Aallam et al. 2021; De Zutter et al. 2022). Soil is the hotspot for diverse microflora. Phosphorus solubilizers are the microorganisms that have ability of changing locked form of P in to a plant accessible form (Chawngthu et al. 2020; Silva et al. 2023; Khan et al. 2024). Their potency for solubilization of P can be analysed via both qualitative and quantitative approach (Mehta and Nautiyal 2001). These PSMs are diversified in nature, bacteria from the genera Serratia, Leclercia adecarboxylata, Enterobacter, Pantoea, Bacillus, Pseudomonas, Arthrobacter and fungi like Aspergillus niger, Penicillium spp, Acremonium, Hymenella and Neosartorya are potent PSMs (Kirui et al. 2022; Biswas et al. 2018; Bashir et al. 2018a, b; Zhang et al. 2019; Teng et al. 2019a; Ichriani et al. 2018; Rojas et al. 2018; Sulbaran et al. 2009). Phosphate solubilizers have been reported as N2 fixers and regulate plant hormone levels (Unnikrishnan and Binitha 2024). There are various reports on isolation and characterization of diverse phosphorus solubilizers from different environmental sources. These PSMs by their metabolic activities perform a dynamic role in soil. These microbes act as potent biofertilizers that enhance agriculture produce and maintain soil fitness (Rajwar et al. 2018).

Phosphorus solubilizers produce various hormones like auxins, cytokinins, gibberellins that enhance seed germination, cell differentiation, shoot elongation and flowering (Puri et al. 2020). An innovative choice strain like Pseudomonas plecoglossicida isolated from rhizospheric soil of soybean, also produced growth promoting hormones like Indole-3-Acetic Acid (IAA) (Astriani et al. 2020). Studies suggested that Trichoderma harzianum can also solubilize P, the strain produced IAA, improved root and shoot biomass, leaf number and size observed on Solanum lycopersicum L. (Bader et al. 2020). Various microorganisms, including bacteria and fungi, are known for their ability to produce organic acids. Pseudomonas produces gluconic acid to increase phosphate solubility, which has become an important technology for improving phosphate fertilizer management in modern agriculture (Wang et al. 2022; Rai et al. 2023). Here are some common organic acids and the microorganisms that often produce them (Table 2).

Table 2 List of microbes secreting organic acids
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3 Mechanisms of Inorganic Phosphorus Solubilization

The PSMs uses various strategies for phosphorus solubilization. Out of which the principal mechanism is low molecular weight (MW) secretions which include organic acids (Citric acid, Malic acid, Gluconic acid, and Oxalic acid) (Saeid et al. 2018; Marra et al.2015; Buch et al. 2008; Liu et al. 2024).Gluconic acid is the main acid secreted by these PSMs (Zhang et al. 2023a, b).The generation of these low MW secretions `causes acidification of microbial cells as well as its surroundings (Lin et al. 2006; Chen et al. 2006; Silva et al. 2023; Khan et al. 2024). Subsequent ionization of acid occurs, and proton released becomes responsible for expelling phosphorus from phosphate via proton substitution for calcium, aluminium, and iron or chelate cations from carboxylic anions and releasing phosphate anions (Aliyat et al. 2022). The release of organic acids has also been well established (Park et al. 2009; Lin et al. 2006). Studies suggested that there occur some genes which are indirectly or directly involved in secretions of these low molecular weight organic acids (Babu-Khan et al. 1995; Buch et al. 2010; Pang et al. 2024). The -COOH and -OH functional groups of these acids compete with Ca2+, Al3+ and Fe2+, make bonds with metal ions (chelation) and thus transforms phosphorus from insoluble to soluble state (Kpomblekou and Tabatabai 1994). The estimation of these compounds (acids) can be done by HPLC (Wei et al. 2017; Park et al. 2009).Siderophores i.e., Fe2+ chelating agents, phosphatases and extracellular polysaccharides (EPS) synthesized by PSBs results in availability of P in its soluble form from fixed phosphate form (Sharma et al. 2013; Yi et al. 2008; Chen and Arai 2023; Thampi et al. 2023). Thus, the various chelating agents, low molecular weight organic acids and enzymes produced by PSMs are main compounds that cause solubilization of inorganic phosphorus.

4 Mechanism Involved in Organic Phosphorus Mineralization

Organic matter is the key basis of phosphorus availability in the soil, various organic phosphorus compounds are nucleic acids, phospholipids, and phosphodiesters and so on (Rodríguez and Fraga 1999). Besides pesticides, antibiotics, that are released in to the environment also contain organic phosphorus. Phosphorus mineralization means solubilization of organic phosphorus. Microorganisms solubilize P by secretion of various enzymes as among them are those that dephosphorylate the phosphorester or phosphoanhydride bond in organic compounds. PSM, mostly release phosphomonoesterases or phosphatases (Nannipieri et al. 2011), these enzymes i.e., phosphomonoesterases can occur in both acidic as well as in alkaline forms (Jorquera et al. 2011). Other class of enzyme secreted by phosphate solubilizers in the process of mineralization of organic P is phytase (Silva et al. 2023; Khan et al. 2024). This phytase enzyme releases the phosphorus from organic materials like plant seeds and pollen. The phytase during degradation process releases phosphorus in a form which is available for plant uptake (Richardson and Simpson 2011).

5 Phosphate Solubilizers as Plant Growth Enhancers

Microorganisms that solubilize phosphates exert indirect or direct influences on plant health and their yield (Zveushe et al. 2023). Direct process comprises improved solubilization of minerals such as K, P, Si and Zn etc. (Prakash and Arora 2019; Bashir et al. 2017; Hayat et al. 2010). The substances /chemicals released by PSB that enhance plant growth are mentioned in (Table 3).

Table 3 Plant growth promoting substances released by phosphorus solubilizing bacteria
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The PSBs have showed good performance for plant development (Prakash and Arora 2019; Wen et al. 2019). These phosphate solubilizing microbial strains increase plant health and yield as they improve the biogeochemical cycling (Fig. 1) (Mitra et al. 2020; Hutchins et al. 2019), prevents from pathogen infestation (Bononi et al. 2020; Saravana et al. 2008), yield some vitamins like riboflavin, biotin, niacin etc., for plant development (Jaiswal et al. 2021; Revillas et al. 2000), phytohormones (Mažylytė et al. 2022; Kalayu 2019; Prakash and Arora 2019), and iron scavenging molecules (Purwaningsih et al. 2021; Prakash and Arora 2019) (Table 4).

Fig. 1
figure 1

Phosphorus solubilizing microbes with different plant growth promoting potential

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Table 4 Phosphorus solubilizing bio-inoculants and their benefited crops
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6 Phosphate Solubilizing Microbes as Biocontrol Agents

Increased application of chemical pesticides has given rise to environmental contamination, reduced beneficial soil biota, and enhanced vulnerability of crops to disease (Yatoo et al. 2021, 2022). The strategy to combat disease is currently being explored, with a focus on using PSMs as biological control agents. In addition to giving plants vital nutrients, PSMs operate as plant growth-promoters and hinder the growth of a variety of diseases, including nematodes (Thomas et al. 2005; Khan and Kounsar 2000; Oyekanmi et al. 2008; Khan et al. 2009a, b, c). PSMs are efficient biocontrol agent for plant diseases. They affect directly different stages of development in nematodes; eggs, larvae and adults (Pocasangre et al. 2007; Pant and Pandey 2001; Oyekanmi et al. 2008; Sharon et al. 2009).

A PSB, Bacillus amyloliquefaciens can inhibit the growth of F. oxysporum can prevent the growth of F. oxysporum through the production of antifungal components 1-amino-cyclo-propane-carboxylic-aciddeaminase, and enzymes like chitinase and cellulase (Gowtham et al. 2016). Chitinase enzymes can inhibit F. oxysporum attack on chilli seeds (Suryanto et al. 2014), and G. philippii (Widyastuti and Sumardi 1998) causing red roots in acacia plants.

Several bacteria from the genera Azotobacter, Pseudomonas and Bacillus are recognised to be vital in the solubilization of soil minerals and to inhibit plant diseases (Khan et al. 2005; Mardhiansyah 2011; Gill et al. 2016; Bashir et al. 2017; Bashir et al. 2018a; Prihatini et al. 2018; Bashir et al. 2018b; Bashir et al. 2019a, b., Bashir et al.2019b; Gowtham et al. 2016). To suppress parasitic nematodes, different phosphate solubilizing bacteria were used in various plants. For example Azospirillum lipoferum was used against Meloidogyne incognita in green gram (Vigna radiata) (Khan and Kounsar 2000), Bacillus subtilis was used against Rootknot nematode (Meloidogyne spp.) of tomato (Solanum lycopersicum) (Jiménez-Aguirre et al. 2023), Pseudomonas fluorescens against Heterodera schachtii in sugar beet (Beta vulgaris) Oostendrop and Sikora (1989), B. subtilis was used against M. incognita in ornamental plants (Khan et al. 2005b), P. fluorescens was used against Heterodera schachtii in sugar beet, Beijerinkia indica was used against M. incognita in green gram (Khan and Akram 2000; Khan et al. 2009a, b, c). These bacteria suppress nematode pathogenesis, as well as encourage plant development by solubilizing minerals in the soil (Khan et al.2009a, b, c).

Phosphate solubilizing bacteria suppress the growth of plant pathogens by adapting different mechanisms. Bacteria gets attached to roots by means of pili in case of Pseudomonas fluorescens on wheat roots (Patil et al. 2002; Khan et al. 2009a, b, c) or involve development and multiplication on the root surface. Various antifungal components are also produced by bacteria that are active against various pathogens including nematodes, these include iturin, mycosubtilin, surfactin, bacilysin, fengymycin HCN, mycobacilin, ammonia, 2,4-diacetylphloroglucinol, xantobaccin, butyrolactones, oomycin, kanosamine, oligomycin, phenazine-1-carboxylicacid, viscosinamide, pyrrolnitrin, zwittermycin A etc. (Khan et al. 2009a, b, c). They stimulate the systemic resistance (SR) in the host against the pathogenic microbes. After inoculating with the biocontrol bacteria, they bring the following changes in the host; increased the level of enzymes like phenylalanine ammonia lyase, polyphenol oxidase, peroxidase and chitinase (M’Piga et al. 1997; Chen and Dickson 2004; Mansoor et al. 2023a), increased production of phytoalexins, enhanced gene expression related to response to stress, deposition of barriers and strengthening of cell walls outside infection sites including phenolics, lignin and cellulose (Khan et al. 2009a, b, c). Bacteria produce a large number of siderophores or iron chelators that have high affinity for iron. They sequester the iron present in the rhizosphere making it inaccessible to pathogens, thus limiting their growth (Khan et al. 2009a, b, c). P. fluorescens and B. subtilis promote growth of plants directly as well as indirectly. Growth promotion via indirect means is based on the suppression of plant parasites (soil borne) and pathogenic microorganisms in the rhizosphere, whereas direct growth promotion is primarily exerted through the release of growth factors. B. subtilis and P. fluorescence synthesizes plant growth promoting hormones such as gibberellins, indole acetic acid, zeatin and cytokinins that enhances plant growth (Khan et al. 2009a, b, c).

Various P solubilizing fungi inhibits the growth of various microbes including nematodes (Khan and Kounsar 2000; Oyekanmi et al. 2008) and other pathogenic fungi (Padmavathi and Madhumathi 2009). In addition to supplying vital nutrients in plants (Thomas et al. 2005), imparts a vital role on solubilizing insoluble phosphorus (Turan 2006) allowing plants to use it (Mittal et al. 2008; Oyekanmi et al. 2008; Khan and Kounsar 2000). Some fungi Aspergillus niger, Penicillium digitatum, Penicillium anatolicum, Trichoderma viride and Trichoderma harzianum, play a major part in phosphate solubilisation and have been used in biomanagement of different pathogenic fungi and nematodes in different plants like A. niger was used in controlling Meloidogyne incognita in tomato (Tayade et al. 2019), okra (Sharma et al. 2005), Paecilomyceslilacinus was used in controlling Meloidogyne spp. in tomato (Schenek 2004), tobacco, P. anatoticum was used in controlling Globodera rostochinensis in potato (Jatala 1986), Trichoderma harzianum, and P. lilacinus was used in controlling M. incognita in chickpea (Pant and Pandey 2001), Trichoderma harzianum and Pseudomonas fluorescens against M. javanica in tomato (Siddiqi and Shaukat 2004). The many developmental stages of nematodes, including eggs, larvae, and adults, may be directly impacted by phosphorus solubilizing fungi (PSF) (Pocasangre et al. 2007, Pant and Pandey 2001; Oyekanmi et al. 2008; Sharon et al. 2009). Trichoderma, a main biocontrol fungus is found in almost all soils and in a diversity of habitats. They are the most common culturable fungi found in soil and colonize plant roots. Trichoderma sp. invade, parasitize, or feed on other fungi. Because it is usually abundant in healthy roots, they evolved many mechanisms to combat other fungi and encourage the growth of plants and roots (Benítez et al. 2004).

The effect of Trichoderma harzianum on different isolates of Xanthomonas was studied and it was observed that Xanthomonas was completely lysed by T. harzianum and inhibited their growth (Padmavathi and Madhumathi 2009). The phosphate-solubilizing fungi adapt different mechanisms to suppress plant pathogens. According to Lipping et al. (2008), antibiosis gives phosphate-solubilizing fungus species of Trichoderma, Penicillium and Aspergillus, a competitive saprophytic advantage. Different species of Trichoderma and Aspergillus produce low molecular weight compounds both volatile and non-volatile that impedes the growth of harmful microbes including in the root zone. Some of the compounds produced by Aspergillus sp. and Trichoderma sp. include harzianic acid, viridin, tricholin, alamethicins, glisoprenins, peptaibols, massoilactone, heptelidic acid, antibiotics, 6-penthyl-pyrone, oxalic acid, gliovirin, and enzymes (Khan et al. 2009a, b, c).

It is believed that the antagonistic action of phosphorus dissolving fungus, like strains of Trichoderma, A. niger and P. digitatum, on the invading pathogen allows them to defend plants against various pathogens (Khan et al. 2009a, b, c). Trichoderma strains have the potential to cause plants to exhibit hypersensitive reactions systemic generated resistance as well as acquired systemic resistance (Harman et al. 2004). Different species of Trichoderma induces resistance in their host by stimulating the production of genes that stimulate the production of phytoalexins, Pathogenesis-related (PR) proteins and other chemicals that increase plant pathogen resistance. Trichoderma harzianum induced resistance in various plants like cucumber, bean, and cotton (Khan et al. 2009a, b, c). Trichoderma releases growth factors that enhance plant growth, crop yield as well as seed germination rates (Benítez et al. 2004). Trichoderma sp and A. niger also produces phytohormones like zeatin and gibberellic acid, and their production might enhance bio fertilization. Thus, with increased nutrient absorption and the synthesis of these plant hormones directly influence plant development, control of different pathogens and enhancing defence mechanism of plants (Khan et al. 2009a, b, c).

7 Phosphate Solubilizers and Bioremediation

Bioremediation has fascinated a lot of scientific attention in recent years. Its mechanisms are based on redox transformations, absorption, and changes in the reaction of the medium. Presently, the most common methods of microbial removal of heavy metals are bioleaching, biomeneralization, biosorption, bioaccumulation, and production of biosurfactants, oxidation–reduction, and biovolatilization (Rahman and Singh 2020). Some specific genera of microorganisms called extremophiles are involved in such processes, these specific microbial strains, are able to develop protective systems to avoid negative effects of heavy metal based pollution. Therefore, the ability of microorganisms to remain viable under the influence of heavy metals in the restoration of disturbed areas is of pivotal importance (Ayangbenro and Babalola 2017; Hamid et al. 2023a, b). According to literature data, it is possible to use Bacteroidetes and Firmicutes for As-contaminated areas. Their abundance positively correlates with this pollutant in contaminated areas. It is also noted that proteobacteria are resistant to high concentrations of Zn, as well as Pb (Fajardo et al. 2019). Under the heavy metal stress some microbial strains are able to secrete or release extracellular substances such as proteins, polysaccharides, lipids containing various heavy metal binding sites (Tarfeen et al. 2022). Diverse phosphate solubilizing microbial communities have been reported which play important role in heavy metal remediation.

Considerable attention is being given to the microbial breakdown of agricultural chemicals such as pesticides, insecticides, fungicides, chemical fertilizers, and other toxic compounds (Rafa and Chiampo 2021). Besides this microbial community benefit the plants by direct or indirect way like phosphate solubilization, potassium solubilization, zinc solubilization, silicate solubilization, nitrogen fixation, 1-aminocyclopropane-1-carboxylate deaminase (ACCD) production, HCN, siderophore (iron chelating agents) production and phytohormone secretions (Glick et al. 2007; Bashir et al. 2017, 2018a, b; Gouda et al. 2018; Kalam et al. 2020; Park et al. 2021; Saeed et al. 2021; Kaur et al. 2024).

Several research reports have shown that PSMs strains including Bacillus spp, Azospirillum lipoferum, Pseudomonas fluorescence, Rhizobium spp that remediate chemicals and also secrete gibberellic acid (GBA) that induce plant health (Bottini et al. 2004; Gouda et al. 2018). These rhizobacterial phosphate solubilizers also secrete EPS which showed effect on growth and development of plant and drought tolerance (Naeem et al. 2018; Bashir et al. 2021; Kaur et al. 2024). Numerous plant growth-promoting features of phosphate solubilizers such as organic acid production (citric, malic, oxalic, propionic acids), secretion of iron chelating agents (siderophores), indole acetic acid production and ACC deaminase activity enhances the phytoremediation capability of plants (Park et al. 2009; Cui et al. 2022). Plentiful P solubilizing strains belonging to the genera of Pseudomonas, Bacillus, Paenibacillus, Brevibacterium, and Staphylococcus have been reported to solubilize phosphate as well as dissolves the Lead (Pb) mineral. PSM in addition to chelating agent Ethylene diamine tetra acetic acid when added to Arsenic contaminated soil, phytoremediation property of Echinochloa frumentacia is enhanced and it has been reported within 85 days from the seeding of Echinochola frumentacia, arsenic contamination in the soil decreases when compared with initial concentration (Yahaghi et al. 2018). Inoculation with both Brevibacterium frigoripolerans YSP40 and Bacillus paralicheniformis YSP151 and their consortium have been reported to enhance the growth and Pb uptake of Brassicajuncea plants grown in metal contaminated soil. Hence, phosphate solubilizers have an effective role to play in bioremediation (Yahaghi et al. 2018).

8 Conclusion

Phosphorus is an indispensable mineral element amongst the macronutrients needed for different plant metabolic functions. Phosphorus is available in soil as inorganic as well as in organic form, but due to its limited accessibility since it occurs in an insoluble form. Because of its complex formation and meagre soil solubility only few percent of total phosphorus are available to plants. Phosphorus accounts for around 0.2–0.8% of the dry weight of the plant. To fulfil the needs of crop nutrition, phosphorus is generally added to soil in chemical form but the synthesis of phosphorus fertilizer is expensive and effortful process. In addition, plants utilize a small quantity of this phosphorus and 75–90% of added phosphorus forms metal-cation complexes, gets precipitated and is quickly locked in soils. Microbiologists and experts in soil science have setup a way to make phosphorus available to crops, a replacement for crop fertilization that is economically successful. Such ecological concerns result in exploration of crop nutrition for a sustainable way of phosphorus. In this regard, Phosphorus solubilizing microorganism is seen as the best environmentally sustainable means for crop phosphorus nutrition, which farmers can afford. Bioremediation being an interesting and highly applied tool for decontamination of heavy metal polluted soils and sits, number of microbes possess remediation capacity and are utilized at large scale. Phosphorus solubilizing microorganisms has proven to be a potential bio-remediating agent and can be applied in agriculture soils for solubilisation as well as remediation purpose. Future insight about improving bioremediation potential of phosphorus solubilizing microorganisms need to be explored for enhancing quality of soil health and plant health.