Analyzing plant growth promoting Bacillus sp. and related genera in Mizoram, Indo-Burma biodiversity Hotspot

Effect of <i>Bacillus thuringiensis</i> strains on growth and metabolic processes in <i>Pisum sativum</i> L. sprouts

Although the entomopathogenic bacteria Bacillus thuringiensis Berliner are well-known bio-agents for regulating the population of leaf-eating pests of agricultural and ornamental crops, other agricultural properties of this microorganism are promising. In this work, the growth-stimulating effect of entomopathogenic strains of B. thuringiensis on Deviz pea plants was studied. The entomopathogenic strains B. thuringiensis 685, 926 and 109-C obtained from the Crimean Collection of Microorganisms of the Crimean Agricultural Research Institute, registered online (http://www.ckp-rf.ru) with number 507484, were used as research material. The morphometric parameters of pea sprouts were evaluated following standard methods. Biochemical parameters of pea sprouts were determined for 10-day-old sprouts. The amylase activity of pea sprouts was determined by photocalorimetry; total acidity was measured by titration using 0.1 n NaOH solution; total water-soluble phenolic compounds were determined by Leventhal titrimetric method. It was found that liquid spore culture of strains B. thuringiensis 685, 926 and 109-C had a stimulating effect on the length of root and stem and the weight of 10-day-old sprouts of Deviz pea variety. Treatment with a spore suspension of all tested strains B. thuringiensis led to an increase in the content of organic acids in the sprouts by an average of 12.4% compared with that of the control. Maximum stimulating effect on amylolytic activity and synthesis of phenolic compounds in Deviz pea sprouts was achieved by treating with a spore suspension of the strain B. thuringiensis 926. The amylase activity increased on average by 41.5% when compared to that of the control, while the total content of phenolic compounds in this experiment was 2.3 times higher than that of the control. Therefore, in light of the entomopathogenic properties and the obtained data on the growth-stimulating activity of the strains of B. thuringiensis, it can be concluded that these bacteria have additional potential for their use in agriculture as a bio-agent for plant protection having a complex action.

Lysinibacilli: A Biological Factories Intended for Bio-Insecticidal, Bio-Control, and Bioremediation Activities

Microbes are ubiquitous in the biosphere, and their therapeutic and ecological potential is not much more explored and still needs to be explored more. The bacilli are a heterogeneous group of Gram-negative and Gram-positive bacteria. Lysinibacillus are dominantly found as motile, spore-forming, Gram-positive bacilli belonging to phylum Firmicutes and the family Bacillaceae. Lysinibacillus species initially came into light due to their insecticidal and larvicidal properties. Bacillus thuringiensis, a well-known insecticidal Lysinibacillus, can control many insect vectors, including a malarial vector and another, a Plasmodium vector that transmits infectious microbes in humans. Now its potential in the environment as a piece of green machinery for remediation of heavy metal is used. Moreover, some species of Lysinibacillus have antimicrobial potential due to the bacteriocin, peptide antibiotics, and other therapeutic molecules. Thus, this review will explore the biological disease control abilities, food preservative, therapeutic, plant growth-promoting, bioremediation, and entomopathogenic potentials of the genus Lysinibacillus.

Lysinibacillus xylanilyticus Strain GIC41 as a Potential Plant Biostimulant

To identify Lysinibacillus strains with the potential to function as plant biostimulants, we screened 10 previously isolated Lysinibacillus strains from the rhizosphere and soil for their plant growth-promoting (PGP) effects. In vitro tests showed that all strains produced indole-3-acetic acid. In primary screening, the PGP effects of these strains were assessed on spinach seedlings grown on Jiffy-7 pellets; strains GIC31, GIC41, and GIC51 markedly promoted shoot growth. In secondary screening, the PGP efficacies of these three strains were examined using spinach seedlings grown in pots under controlled conditions. Only GIC41 exerted consistent and significant PGP effects; therefore, it was selected for subsequent experiments. The results of 6-week glasshouse experiments revealed that GIC41 markedly increased shoot dry weight by ca. 12–49% over that of the control. The impact of fertilization levels on the PGP efficacy of GIC41 was investigated using pot experiments. The application of a specific level of fertilizer was required for the induction of sufficient PGP effects by this strain. The phylogenetic ana­lysis based on the 16S rDNA sequence identified GIC41 as L. xylanilyticus. Collectively, these results show the potential of strain GIC41 to function as a plant biostimulant.

Characterization of Lysinibacillus fusiformis strain S4C11: In vitro, in planta, and in silico analyses reveal a plant-beneficial microbe

Despite sharing many of the traits that have allowed the genus Bacillus to gain recognition for its agricultural relevance, the genus Lysinibacillus is not as well-known and studied. The present study employs in vitro, in vivo, in planta, and in silico approaches to characterize Lysinibacillus fusiformis strain S4C11, isolated from the roots of an apple tree in northern Italy. The in vitro and in vivo assays demonstrated that strain S4C11 possesses an antifungal activity against different fungal pathogens, and is capable of interfering with the germination of Botrytis cinerea conidia, as well as of inhibiting its growth through the production of volatile organic molecules. In planta assays showed that the strain possesses the ability to promote plant growth, that is not host-specific, both in controlled conditions and in a commercial nursery. Biocontrol assays carried out against phytopathogenic viruses gave contrasting results, suggesting that the strain does not activate the host's defense pathways. The in silico analyses were carried out by sequencing the genome of the strain through an innovative approach that combines Illumina and High-Definition Mapping methods, allowing the reconstruction of a main chromosome and two plasmids from strain S4C11. The analysis of the genes encoded by the genome contributed to the characterization of the strain, detecting genes related to the biocontrol effect detected in the experimental trials.