Characterization of a novel chitinase from a moderately halophilic bacterium, Virgibacillus marismortui strain M3-23

Exploring Halophiles for Reclamation of Saline Soils: Biotechnological Interventions for Sustainable Agriculture

Soil salinization is a major constraint on agricultural productivity, particularly in arid and semi-arid regions where limited rainfall cannot wash salts from plant root zones. This leads to disruptions in water uptake, ion balance, photosynthesis, respiration, nutrient absorption, hormone regulation and rhizosphere microbiome disturbances in plants. Chemical and biological methods can help mitigate soil salinity, but biological approaches, like using halophytes and salt-tolerant microorganisms, are preferred for environmental sustainability. Halophytes, however, represent only about 1% of flora and are habitat specific, so halophilic plant growth-promoting (PGP) microbes have emerged as a key eco-friendly solution. Halophilic PGP bacteria have shown promise in remediating saline soils, enhancing fertility and boosting crop resilience by inducing salinity tolerance (IST) and promoting plant growth traits. In the era of modern agriculture where chemical inputs are at their peak of application rendering the soil infertile, halophilic PGP bacteria represent a promising, sustainable approach to support food security, aligning with Sustainable Development Goals for zero hunger.

Discovery and characterization of novel lipopeptides produced by Virgibacillus massiliensis with biosurfactant and antimicrobial activities

The study aimed to evaluate the biosurfactants (BSs) production by SM-23 strain of Virgibacillus identified by phenotypical and WGS analysis as Virgibacillus massiliensis. We first demonstrated the lipopeptides production by Virgibacillus massiliensis specie and studied their biochemical and molecular analysis as well as their biological potential. The GC-MS analysis indicated that methyl.2-hyroxydodecanoate was the major fatty acid compound with 33.22%. The maximum BSs production was obtained in LB medium supplemented by 1% olive oil (v/v) at 30 °C and 5% NaCl with 1.92 g/l. The obtained results revealed the significant biosurfactants/bioemulsifier potential compared to triton X100 with E24 of 100%, and an emulsification stability SE of 83%. The lipopeptides types were identified by FTIR analysis. A strong antimicrobial action was observed by the produced lipopeptides by the agar diffusion method against E.coli, K. pneumoniae, S. aureus, Fusarium sp, Alternaria sp, and Phytophtora sp. The complete genome sequencing showed genes involved in the synthesis of multiple compounds identified as amphipathic cyclic lipopeptides such as locillomycin/locillomycin B/locillomycin C and bacillibactin. Our results highlighted significant lipopeptides properties displayed by V. massiliensis that can be exploited to develop a novel strategy in the formulation of natural biocidal and fungicidal agents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04100-9.

Extremozymes and compatible solute production potential of halophilic and halotolerant bacteria isolated from crop rhizospheric soils of Southwest Saurashtra Gujarat

Halophiles are one of the classes of extremophilic microorganisms that can flourish in environments with very high salt concentrations. In this study, fifteen bacterial strains isolated from various crop rhizospheric soils of agricultural fields along the Southwest coastline of Saurashtra, Gujarat, and identified by 16S rRNA gene sequencing as Halomonas pacifica, H. stenophila, H. salifodinae, H. binhaiensis, Oceanobacillus oncorhynchi, and Bacillus paralicheniformis were investigated for their potentiality to produce extremozymes and compatible solute. The isolates showed the production of halophilic protease, cellulase, and chitinase enzymes ranging from 6.90 to 35.38, 0.004-0.042, and 0.097-0.550 U ml-1, respectively. The production of ectoine-compatible solute ranged from 0.01 to 3.17 mg l-1. Furthermore, the investigation of the ectoine-compatible solute production at the molecular level by PCR showed the presence of the ectoine synthase gene responsible for its biosynthesis in the isolates. Besides, it also showed the presence of glycine betaine biosynthetic gene betaine aldehyde dehydrogenase in the isolates. The compatible solute production by these isolates may be linked to their ability to produce extremozymes under saline conditions, which could protect them from salt-induced denaturation, potentially enhancing their stability and activity. This correlation warrants further investigation.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

Polyextremophilic Chitinolytic Activity by a Marine Strain (IG119) of Clonostachys rosea

The investigation for novel unique extremozymes is a valuable business for which the marine environment has been overlooked. The marine fungus Clonostachys rosea IG119 was tested for growth and chitinolytic enzyme production at different combinations of salinity and pH using response surface methodology. RSM modelling predicted best growth in-between pH 3.0 and 9.0 and at salinity of 0-40‱, and maximum enzyme activity (411.137 IU/L) at pH 6.4 and salinity 0‱; however, quite high production (>390 IU/L) was still predicted at pH 4.5-8.5. The highest growth and activity were obtained, respectively, at pH 4.0 and 8.0, in absence of salt. The crude enzyme was tested at different salinities (0-120‱) and pHs (2.0-13.0). The best activity was achieved at pH 4.0, but it was still high (in-between 3.0 and 12.0) at pH 2.0 and 13.0. Salinity did not affect the activity in all tested conditions. Overall, C. rosea IG119 was able to grow and produce chitinolytic enzymes under polyextremophilic conditions, and its crude enzyme solution showed more evident polyextremophilic features. The promising chitinolytic activity of IG119 and the peculiar characteristics of its chitinolytic enzymes could be suitable for several biotechnological applications (i.e., degradation of salty chitin-rich materials and biocontrol of spoiling organisms, possibly solving some relevant environmental issues).

Role of halotolerant and chitinolytic bacteria in phytoremediation of saline soil using spinach plant

Novel technologies are required for rapid reclamation of saline soils. The halotrophic and chitinolytic bacterial strains were used for phytoremediation of saline soils using spinach plants (Spinacia oleracea L.). The previously isolated chitinolytic bacteria showed high antifungal potential against Fusarium oxysporum, and Alternaria spp. The halotolerant bacterial strains were previously isolated showing a salt tolerance of up to 20% in culture media. Specially designed microcosms were used here to investigate the reclamation of saline soil by bacteria. The soil salinity was reduced by both types of bacteria (from 6.5 to 2 dS/m). A decline in Na contents from 22-24 to 9-12 meq/L and in sodium adsorption ratio from 10-11 to 7-8 was also observed in saline soils. The Ca/Mg contents increased from 24 to 30-33 meq/L. The bioassays were performed to evaluate the effect of the bacteria on the phytoremediation. The shoot, root weights (both fresh (1.927 g, 0.244 g) and dry (0.387 g, 0.104 g)) increased by bacterial inoculation as compared to control in saline soils. The Na/K ratio decreased in plant tissues. Here we report the increased efficacy of phytoremediation by combined inoculation of chitinolytic and halotolerant bacterial strains in soil which has never been reported before.

Functional expression and characterization of a chitinase from the marine archaeon Halobacterium salinarum CECT 395 in Escherichia coli

The HschiA1 gene of the archaeon Halobacterium salinarum CECT 395 was cloned and overexpressed as an active protein of 66.5 kDa in Escherichia coli. The protein called HsChiA1p has a modular structure consisting of a glycosyl hydrolase family 18 catalytic region, as well as a N-terminal family 5 carbohydrate-binding module and a polycystic kidney domain. The purified recombinant chitinase displayed optimum catalytic activity at pH 7.3 and 40 °C and showed high stability over broad pH (6-8.5) and temperature (25-45 °C) ranges. Protein activity was stimulated by the metal ions Mg(+2), K(+), and Ca(+2) and strongly inhibited by Mn(+2). HsChiA1p is salt-dependent with its highest activity in the presence of 1.5 M of NaCl, but retains 20% of its activity in the absence of salt. The recombinant enzyme hydrolysed p-NP-(GlcNAc)3, p-NP-(GlcNAc), crystalline chitin, and colloidal chitin. From its sequence features and biochemical properties, it can be identified as an exo-acting enzyme with potential interest regarding the biodegradation of chitin waste or its bioconversion into biologically active products.