γ-Polyglutamic Acid Production, Biocontrol, and Stress Tolerance: Multifunction of Bacillus subtilis A-5 and the Complete Genome Analysis

Abstract

Bacillus subtilis A-5 has the capabilities of high-molecular-weight γ-PGA production, antagonism to plant pathogenic fungi, and salt/alkaline tolerance. This multifunctional bacterium has great potential for enhancing soil fertility and plant security in agricultural ecosystem. The genome size of B. subtilis A-5 was 4,190,775 bp, containing 1 Chr and 2 plasmids (pA and pB) with 43.37% guanine-cytosine content and 4605 coding sequences. The γ-PGA synthase gene cluster was predicted to consist of pgsBCA and factor (pgsE). The γ-PGA-degrading enzymes were mainly pgdS, GGT, and cwlO. Nine gene clusters producing secondary metabolite substances, namely, four unknown function gene clusters and five antibiotic synthesis gene clusters (surfactin, fengycin, bacillibactin, subtilosin_A, and bacilysin), were predicted in the genome of B. subtilis A-5 using antiSMASH. In addition, B. subtilis A-5 contained genes related to carbohydrate and protein decomposition, proline synthesis, pyruvate kinase, and stress-resistant proteins. This affords significant insights into the survival and application of B. subtilis A-5 in adverse agricultural environmental conditions.

Production of poly‐gamma‐glutamic acid and spore formation in Bacillus velezensis 83 are affected by acidic growing conditions and glucose uptake rate

“…Precursor of glutamate is 2-oxoglutarate that is transformed to glutamic acid by glutamate synthase encoded in gltAB genes. 47,48 Some authors have been reported that acidic environments downregulated gltAB. 45 On the other hand, expression of citB gene, encoded for aconitase enzyme, responsible for citrate conversion to isocitrate in the tricarboxylic acid cycle is under control of the AbrB repressor, which is counteracted by sigma-H. As explained earlier, acid conditions would lead to lower sigma-H activity, maintaining AbrB negative control on aconitase, decreasing the carbon flux towards 2-oxoglutarate, the glutamate precursor and hence to γ-PGA.…”

Effects of Bacillus subtilis A-5 and its fermented γ-polyglutamic acid on the rhizosphere bacterial community of Chinese cabbage

“…subtilis was recognized to promote plant growth or biocontrol of soil-borne disease (Balderas-Ruíz et al, 2021 ). In our previous research, strain A-5 was also used as a multifunctional PGPR with biocontrol properties and salt-alkaline resistance (Bai et al, 2022 ). Therefore, A-5 addition (A5 and FJY treatments) significantly altered the bacterial community structure in the rhizosphere soil.…”

Genomic characterization and related functional genes of γ- poly glutamic acid producing Bacillus subtilis

“…Additionally, the glutamate racemase encoded by the pgsA gene facilitates the conversion of L-glutamate-γ-semialdehyde to D-glutamate-γ-semialdehyde [ 2 ]. Ultimately, the multifunctional enzyme encoded by pgsE , possessing glutamate racemase and glutamate-5-semialdehyde dehydrogenase activities, catalyzes the conversion of D-glutamate-γ-semialdehyde to L-glutamate, thereby completing the synthesis of γ-PGA, which is then released extracellularly [ 25 ]. The synthesis of γ-PGA is an ATP-dependent process, and the synthesis of bioprecursors containing glutamic acid residues conveniently provides energy for this process [ 24 ].…”