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Sulfur-oxidizing Bacteria: A Novel Bioinoculant for Sulfur Nutrition and Crop Production
Abstract
Sulfur is an essential nutrient for plant growth as sulfur-deficient conditions cause severe losses in crop yield. Sulfur
nutrition has received little attention for many years, since fertilizers and atmospheric inputs have provided adequate amounts.
However, recent reductions in sulfur inputs from atmospheric depositions have resulted in a negative sulfur balance in agricultural
soils, making crop plants increasingly dependent on the soil to supply sulfur. Thus to alleviate this deficiency, sulfur fertilizers
are invariably added to soils, usually in a reduced form, such as elemental sulfur. Yet, reduced sulfur fertilizers must be
oxidized to sulfate before they become available to the plant, a process that is mediated by microorganisms. Sulfur and sulfur
fertilizers and physiological role of sulfur in crop plants and interaction of sulfur with other elements along with ecological
niches for isolation of sulfur-oxidizing bacteria and their role in sulfur oxidation in soil and sulfur nutrition to crop
plants are discussed.
... Among the three groups, chemolithotrophic SOB, also known as colorless SOB is the most dominant and effective sulfur oxidizers, which includes several species of Thiobacillus, Sulfolobus, Thermothrix, Beggiatoa , and Thiothrix (Tourna et al. 2014 ). Due to their high rate of sulfide oxidation, modest nutritional requirements, and extremely high affinity for sulfides and oxygen, they can successfully compete for the oxidation of sulfides in both natural environments and bioreactors with a limited supply of oxygen (Anandham et al. 2011 ). ...
... denitrificans , and T. thiooxidans ) and long, filamentous bacteria of the genera Beggiatoa and Thiothrix . The long, filamentous bacteria oxidize H 2 S-S 0 (Anandham et al. 2011 ). ...
... Other examples of mixotrophic growth are T. nov ellus , Pseudomonas acidov orans , P. putida , and Thiothrix sp. (Anandham et al. 2011 ). The pattern of food production in chemoautotrophic SOB is illustrated in Fig. 1 . ...
Sulfur (S) deficiency is becoming more common in agro-ecosystems worldwide due to factors such as agronomic practices, high biomass production, reduced sulfur emissions and the use of non-sulfur fertilizers. This review explores the natural occurrence and commercial exploitation of sulfur pools in nature, the mineralization and immobilization of sulfur, the physiological role of sulfur in plants and its deficiency symptoms. Additionally, the organic and inorganic forms of sulfur in soil, their transformations, and the process of microbiological oxidation of sulfur are discussed. The review also addresses the diversity of sulfur-oxidizing bacteria (SOB) and the various biochemical mechanisms involved in their role in plant productivity and soil reclamation. The measurement of S oxidation rate in soil and the variables that influence the process are also examined. Typically, the rate of oxidation of added elemental S is around 40-51%, which is available for plant uptake. These characteristics of SOB demonstrate their potential as bioinoculants for increasing plant growth, indicating their use as biofertilizers for sustainable crop production in agro-ecosystems.
... Another vital element for plant growth and development besides N, P, and K is sulfur (S). It plays a role in photosynthesis, respiration, and the formation of chlorophyll and cell membrane structure in plants, which are related to the quality and yield of crop production [61][62][63]. Plants absorb S as sulfate from the soil, however, soil environments contain sulfate only 1-5% of the total bioavailable sulfur [64]. The sulfur-oxidizing (SOX) system encoded by Sox-ACDXYZ genes was found in the NMS14P genome. ...
A novel methylotrophic bacterium designated as NMS14P was isolated from the root of an organic coffee plant (Coffea arabica) in Thailand. The 16S rRNA sequence analysis revealed that this new isolate belongs to the genus Methylobacterium, and its novelty was clarified by genomic and comparative genomic analyses, in which NMS14P exhibited low levels of relatedness with other Methylobacterium-type strains. NMS14P genome consists of a 6,268,579 bp chromosome, accompanied by a 542,519 bp megaplasmid and a 66,590 bp plasmid, namely pNMS14P1 and pNMS14P2, respectively. Several genes conferring plant growth promotion are aggregated on both chromosome and plasmids, including phosphate solubilization, indole-3-acetic acid (IAA) biosynthesis, cytokinins (CKs) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, sulfur-oxidizing activity, trehalose synthesis, and urea metabolism. Furthermore, pangenome analysis showed that NMS14P possessed the highest number of strain-specific genes accounting for 1408 genes, particularly those that are essential for colonization and survival in a wide array of host environments, such as ABC transporter, chemotaxis, quorum sensing, biofilm formation, and biosynthesis of secondary metabolites. In vivo tests have supported that NMS14P significantly promoted the growth and development of maize, chili, and sugarcane. Collectively, NMS14P is proposed as a novel plant growth-promoting Methylobacterium that could potentially be applied to a broad range of host plants as Methylobacterium-based biofertilizers to reduce and ultimately substitute the use of synthetic agrochemicals for sustainable agriculture.
... Some crop plants, such as canola, have high requirements for sulphur. To alleviate sulphur deficiency in canola, some microbial formulations are applied with elemental sulphur [255]. ...
Conventional farming practices can lead to soil degradation and a decline in productivity. Regenerative agriculture (RA) is purported by advocates as a solution to these issues that focuses on soil health and carbon sequestration. The fundamental principles of RA are to keep the soil covered, minimise soil disturbance, preserve living roots in the soil year round, increase species diversity, integrate livestock, and limit or eliminate the use of synthetic compounds (such as herbicides and fertilisers). The overall objectives are to rejuvenate the soil and land and provide environmental, economic, and social benefits to the wider community. Despite the purported benefits of RA, a vast majority of growers are reluctant to adopt these practices due to a lack of empirical evidence on the claimed benefits and profitability. We examined the reported benefits and mechanisms associated with RA against available scientific data. The literature suggests that agricultural practices such as minimum tillage, residue retention, and cover cropping can improve soil carbon, crop yield, and soil health in certain climatic zones and soil types. Excessive use of synthetic chemicals can lead to biodiversity loss and ecosystem degradation. Combining livestock with cropping and agroforestry in the same landscape can increase soil carbon and provide several co-benefits. However, the benefits of RA practices can vary among different agroecosystems and may not necessarily be applicable across multiple agroecological regions. Our recommendation is to implement rigorous long-term farming system trials to compare conventional and RA practices in order to build knowledge on the benefits and mechanisms associated with RA on regional scales. This will provide growers and policy-makers with an evidence base from which to make informed decisions about adopting RA practices to realise their social and economic benefits and achieve resilience against climate change.
... The relative abundance of aerobic microorganisms of Acidobacteria, Bacteroidetes, and Proteus in low-salt soil was higher than that in high-salt soil. Studies have shown that acidobacteria, Bacteroidetes, and Proteus have hydrocarbon biodegradability (Anandham et al., 2011). The experiment proved that petroleum hydrocarbon content in high-salt soil was higher than that in low-salt soil after 30 days. ...
Saline-alkali is one of the important environmental factors affecting oil-contaminated soil. In order to clarify the influence mechanism of salt content on microbial community of oil-contaminated soil, using 16S rDNA amplicon high-throughput sequencing technology, the composition of microbial community in oil-contaminated soil treated with different salinity (1%, 2%, 3%) were analyzed combined with soil environmental factors, and the variation trend of the abundance of functional genes under salt stress was analyzed. The results showed that salinity (1–3%) was positively correlated with soil microbial diversity and evenness. There were significant differences of dominant genera under different salinity stresses. The dominant bacteria were Halomonas and Dietzia at 1% salinity, Alcanivorax at 2% salinity, and Nocardioides, KCM-B-112, Staphylococcus, Bacillus, and Virgibacillus at 3% salinity. Redundancy analysis (RDA) showed that total petroleum hydrocarbon (TPH) and equivalent carbon were the decisive factors for the differential distribution of microbial communities in oil-contaminated soil. Salinity was significantly negatively correlated with Proteobacteria and Bacteroidota, and positively correlated with Firmicutes, Actinobacteriota, and Chloroflexi. TPH was significantly positively correlated with Chloroflexi, Actinobacteriota, Firmicutes, and Acidobacteriota. The results of KEGG functional annotation showed that salt stress decreased the abundance of genes related to metabolism, genetic information processing, and environmental information processing. In particular, the abundance of menbrance transport, xenobiotics biodegradation and metabolism, energy metabolism, and other genes closely related to membrane transport and degradation of oil hydrocarbon were negatively correlated with salinity. This study provides a basis for elucidating the stress mechanism of salt on microbial remediation of petroleum hydrocarbon–contaminated soil.
... Sulfur-oxidizing Bacteria, such as Thiobacillus spp., can supply plant-available sulfur by oxidizing elemental sulfur (YANG et al., 2010). These sulfur-oxidizing bacteria and their physiological role of sulfur in plants have been discussed (Anandham et al., 2011). ...
Over the past 30 years, the ever-rising demands of the modern and growing population have led to the rapid development of agricultural and industrial sectors worldwide. However, this expansion has exposed the environment to various pollutants including heavy metal (HM)s. Almost all HMs are serious toxicants and can pose serious health risks to living organisms in addition to their bioaccumulative and non-biodegradable nature. Different techniques have been developed to restore the ecological functions of the HM-contaminated soil (HMCS). However, the major downfalls of the commonly used remediation technologies are the generation of secondary wastes, high operating costs, and high energy consumption. Phytoremediation is a prominent approach that is more innocuous than the existing remediation approaches. Some microbes-plant interactions enhance the bioremediation process, with heavy metal resistant-plant growth promoting bacteria (HMRPGPB) being widely used to assist phytoremediation of HMs. However, the most common of all major microbial assisted-phytoremediation disturbances is that the HM-contaminated soil is generally deficient in nutrients and cannot sustain the rapid growth of the applied HMRPGPB. In this case, biochar has recently been approved as a potential carrier of microbial agents. The biochar-HMRPGPB-plant association could provide a promising green approach to remediate HM-polluted sites. Therefore, this review addresses the mechanisms through which biochar and HMRPGPB can enhance phytoremediation. This knowledge of biochar-HMRPGPB-plant interactions is significant with respect to sustainable management of the HM-polluted environment in terms of both ecology and economy, and it offers the possibility of further development of new green technologies.
... Plants uptake sulfur in the form of sulfate from the soil solution. Sulfur oxidizing bacteria (SOB) is the leading cause for the oxidation of applied sulfur into the soil to SO 4 2À (Anandham et al. 2011;Mikkelsen and Norton 2013). SOB obtain electron for chemoautotrophic growth and biomass production by oxidation of different sulfur compounds (thiosulfate, elemental sulfur, thiocyanate, Tetrathionate, etc) to sulfate (Christel et al. 2016;Wang et al. 2018). ...
Salinity negatively affects growth of sulfur-oxidizing bacteria (SOB) and their sulfate production ability, meanwhile decreases the available sulfate for plants in soil. The aim of this study was to isolate and characterize the bacteria of genus Halothiobacillus, as a salt-tolerant SOB, from saline and sulfidic habitats of Iran for the first time and evaluating the effect of salinity on their biomass and sulfate production during the oxidation of different sulfur sources. Isolation process and surveying the morphological, biochemical and 16S rRNA gene analysis resulted into identification of three species (eight strains) of Halothiobacillus genus including H. neapolitanus, H. hydrothermalis and H. halophilus. Salinity (0, 0.5, 1, 2 and 4 M NaCl) had a significant impact (p ≤ 0.01) on bacterial biomass and sulfate production during the oxidation of thiosulfate and elemental sulfur. Biomass and sulfate production by strains was accompanied by a decrease in residual content of thiosulfate (RCT) in medium. The amount of produced biomass and sulfate in medium supplemented by thiosulfate was much higher than elemental sulfur. The highest amount of biomass and sulfate was produced by H. neapolitanus strain I19 at 0.5 and 1 M NaCl concentration. The results of this study could be the first step to focus on the application of these bacteria to increase sulfate storage of saline soils and crop production.
... With regard to the family Thermodesulfobacteriaceae, Thermodesulfobacterium was the only genus with sulfate and thiosulfate-reducing ability . In addition, a large amount of sulfur-oxidizing bacteria (SOB) including Bosea, Methylobacterium, Paracoccus, Pseudomonas and Halomonas were found in the active community, which obtained energy by oxidizing reduced sulfur compounds (Anandham et al., 2011;Friedrich et al., 2001;Telegdi et al., 2017). Of these genera, the type species of the Bosea genus (Bosea thiooxidans) was isolated from agricultural soil and had the ability to convert thiosulfate to sulfate (Das et al., 1996). ...
Microbial activity is ubiquitous and important in petroleum reservoir systems; however, current knowledge regarding the diversity and functions of microbial communities that are active in offshore petroleum reservoirs remains very limited. In the present work, high-throughput sequencing analysis of the 16S rRNA gene (DNA) and transcripts (RNA) was applied to respectively characterize the genomic and active microbial communities from two production wells in a high-temperature offshore oilfield in China. The results showed that the microbial community compositions in the two wells (X1 and X2) were very different. At the genus level, the dominant members in both genomic and active communities of sample X1 were Bosea, Acinetobacter, Sphingomonas, Candidatus Methanofastidiosum and Methanocalculus. Both genomic and active communities in sample X2 were mainly represented by Pseudomonas, Acinetobacter, Methanothermobacter, Methanosaeta, Candidatus Nitrosopumilus, Candidatus Methanomethylicus, Thermococcus, Candidatus Methanofastidiosum and Methanocalculus. Moreover, using an RNA-based approach, genera with a very low abundance and even undetected genera (based on a DNA approach) were shown to have increased activity. Besides the abundant active members, the comparison between the DNA- and RNA-based datasets also permitted the identification of genera that were relatively more active in the two production water samples. The existence of these active microorganisms suggested they might have potential functions associated with reservoir issues in the offshore oilfield. This study highlights the importance of assessing microbial diversity through a combination of DNA- and RNA-based analyses, and promotes a comprehensive and deep understanding of microbial compositions and their roles in offshore petroleum reservoirs.
... Sulfur-oxidising bacteria such as Thiobacillus spp. increase the sulphur oxidation rate and produce sulphates that can then be taken up by plants (Anandham et al. 2011; Smyth et al. 2011; Mohamed et al. 2014). ...
One of the major issues facing humankind is global food security. A changing climate, coupled with a heightened consumer awareness of how food is produced and legislative changes governing the usage of agrichemicals for improving plant health and yield, means that alternative, more integrated and sustainable approaches are needed for crop management practices. To this end, there is increasing recognition of the value of the role of microbial inoculants in agriculture. The focus of this review is to understand how plant-growth-promoting bacteria and arbuscular mycorrhizal fungi can play a part in improving crop yield by promoting the health status of the plant through the sequestration of various nutrients and in the control of plant diseases.
The contamination of soil with organic pollutants has been accelerated by agricultural and industrial development and poses a major threat to global ecosystems and human health. Various chemical and physical techniques have been developed to remediate soils contaminated with organic pollutants, but challenges related to cost, efficacy, and toxic byproducts often limit their sustainability. Fortunately, phytoremediation, achieved through the use of plants and associated microbiomes, has shown great promise for tackling environmental pollution; this technology has been tested both in the laboratory and in the field. Plant−microbe interactions further promote the efficacy of phytoremediation, with plant growth-promoting bacteria (PGPB) often used to assist the remediation of organic pollutants. However, the efficiency of microbe-assisted phytoremediation can be impeded by (i) high concentrations of secondary toxins, (ii) the absence of a suitable sink for these toxins, (iii) nutrient limitations, (iv) the lack of continued release of microbial inocula, and (v) the lack of shelter or porous habitats for planktonic organisms. In this regard, biochar affords unparalleled positive attributes that make it a suitable bacterial carrier and soil health enhancer. We propose that several barriers can be overcome by integrating plants, PGPB, and biochar for the remediation of organic pollutants in soil. Here, we explore the mechanisms by which biochar and PGPB can assist plants in the remediation of organic pollutants in soils, and thereby improve soil health. We analyze the cost-effectiveness, feasibility, life cycle, and practicality of this integration for sustainable restoration and management of soil.
The indiscriminate as well as imbalanced application of inorganic fertilizers and climate change associated land degradation negatively affected the soil’s physical, chemical, and microbiological characteristics, thereby affecting global food production. In soils, various microbial communities are involved in nutrient transformations, thereby determining the mobilization, and fixation capacity of nutrients impacting crop growth and development. Some bacterial and fungal genera are involved in a number of mechanisms such as organic acid production, proton extrusion, critical enzyme production that enables the transformation of unavailable forms of nutrients into available forms. Furthermore, the definitive role of different soil abiotic and biotic components also determines the fate of the nutrient transformation and its availability to the plants by affecting the microbial community structure as well as diversity. Taking sustainability into consideration, the exploitation of microbial inoculants to increase the availability of essential plant nutrients could be a viable alternative option for increasing food productivity without compromising soil quality. In this chapter, we discussed the role of diverse microbial communities in nutrients transformation of major (nitrogen, phosphorus, potassium, sulfur) and minor elements (iron, manganese, and copper), their mechanism, and their key roles in plant and soil health, and the conditions favouring the availability of nutrients are elucidated in detail.
Denitrification is a distinct means of energy conservation, making use of N oxides as terminal electron acceptors for cellular bioenergetics under anaerobic, microaerophilic, and occasionally aerobic conditions. The process is an essential branch of the global N cycle, reversing dinitrogen fixation, and is associated with chemolithotrophic, phototrophic, diazotrophic, or organotrophic metabolism but generally not with obligately anaerobic life. Discovered more than a century ago and believed to be exclusively a bacterial trait, denitrification has now been found in halophilic and hyperthermophilic archaea and in the mitochondria of fungi, raising evolutionarily intriguing vistas. Important advances in the biochemical characterization of denitrification and the underlying genetics have been achieved with Pseudomonas stutzeri, Pseudomonas aeruginosa, Paracoccus denitrificans, Ralstonia eutropha, and Rhodobacter sphaeroides. Pseudomonads represent one of the largest assemblies of the denitrifying bacteria within a single genus, favoring their use as model organisms. Around 50 genes are required within a single bacterium to encode the core structures of the denitrification apparatus. Much of the denitrification process of gram-negative bacteria has been found confined to the periplasm, whereas the topology and enzymology of the gram-positive bacteria are less well established. The activation and enzymatic transformation of N oxides is based on the redox chemistry of Fe, Cu, and Mo. Biochemical breakthroughs have included the X-ray structures of the two types of respiratory nitrite reductases and the isolation of the novel enzymes nitric oxide reductase and nitrous oxide reductase, as well as their structural characterization by indirect spectroscopic means. This revealed unexpected relationships among denitrification enzymes and respiratory oxygen reductases. Denitrification is intimately related to fundamental cellular processes that include primary and secondary transport, protein translocation, cytochrome c biogenesis, anaerobic gene regulation, metalloprotein assembly, and the biosynthesis of the cofactors molybdopterin and heme D1. An important class of regulators for the anaerobic expression of the denitrification apparatus are transcription factors of the greater FNR family. Nitrate and nitric oxide, in addition to being respiratory substrates, have been identified as signaling molecules for the induction of distinct N oxide-metabolizing enzymes.
This chapter discusses sulfur amino acids in plants. Most of the inorganic sulfate assimilated and reduced by plants appears ultimately in cysteine and methionine. These amino acids contain about 90% of the total sulfur in most plants. Nearly all of the cysteine and methionine is in protein. The chapter highlights the typical dominance of protein cysteine and protein methionine in the total organic sulfur. In the nonprotein fraction, reduced glutathione (GSH) is ubiquitous and is commonly a major constituent. The soluble fraction of plants also includes a variety of other sulfur-containing compounds that are normally present in relatively small amounts: (1) intermediates on the route to protein cysteine and protein methionine, such as cysteine, cystathionine, homocysteine, and methionine and (2) compounds involved in methyl transfer reactions and polyamine synthesis such as AdoMet, AdoHcy, and 5'-methyl-thioadenosine. Cysteine is the precursor of protein cysteine, GSH, and the sulfur moiety of methionine and is, therefore, the major portal for organic reduced sulfur. Serine is the source of the C3 moiety of cysteine in plants.
The polyketide metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) is produced by many strains of fluorescent Pseudomonas spp. with biocontrol activity against soilborne fungal plant pathogens. Genes required for 2,4-DAPG synthesis by P. fluorescens Q2-87 are encoded by a 6.5-kb fragment of genomic DNA that can transfer production of 2,4-DAPG to 2,4-DAPG-nonproducing recipient Pseudomonas strains. In this study the nucleotide sequence was determined for the 6.5-kb fragment and flanking regions of genomic DNA from strain Q2-87. Six open reading frames were identified, four of which ( phlACBD ) comprise an operon that includes a set of three genes ( phlACB ) conserved between eubacteria and archaebacteria and a gene ( phlD ) encoding a polyketide synthase with homology to chalcone and stilbene synthases from plants. The biosynthetic operon is flanked on either side by phlE and phlF , which code respectively for putative efflux and regulatory (repressor) proteins. Expression in Escherichia coli of phlA , phlC , phlB , and phlD , individually or in combination, identified a novel polyketide biosynthetic pathway in which PhlD is responsible for the production of monoacetylphloroglucinol (MAPG). PhlA, PhlC, and PhlB are necessary to convert MAPG to 2,4-DAPG, and they also may function in the synthesis of MAPG.
Plant hormones play a crucial role in controlling the way in which plants growand develop. Whilemetabolism providesthepowerand buildingblocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, theyplayacontrolling role inthe processes of reproduction. This book is a description ofthese natural chemicals: how they are synthesizedand metabolized; howthey work; whatwe knowoftheir molecular biology; how we measure them; and a description ofsome ofthe roles they play in regulating plant growth and development. Emphasis has also been placed on the new findings on plant hormones deriving from the expanding use ofmolecular biology as a tool to understand these fascinating regulatory molecules. Even at the present time, when the role of genes in regulating all aspects of growth and development is considered of prime importance, it is still clear that the path of development is nonetheless very much under hormonal control, either via changes in hormone levels in response to changes in gene transcription, or with the hormones themselves as regulators ofgene transcription. This is not a conference proceedings, but a selected collection ofnewly written, integrated, illustrated reviews describing our knowledge of plant hormones, and the experimental work that is the foundation of this knowledge.
An understanding of the mineral nutrition of plants is of fundamental importance in both basic and applied plant sciences. The Second Edition of this book retains the aim of the first in presenting the principles of mineral nutrition in the light of current advances. This volume retains the structure of the first edition, being divided into two parts: Nutritional Physiology and Soil-Plant Relationships. In Part I, more emphasis has been placed on root-shoot interactions, stress physiology, water relations, and functions of micronutrients. In view of the worldwide increasing interest in plant-soil interactions, Part II has been considerably altered and extended, particularly on the effects of external and interal factors on root growth and chapter 15 on the root-soil interface. The second edition will be invaluable to both advanced students and researchers.