Draft Genome Sequence of Plant Growth-Promoting Bacillus altitudinis Strain PAE4

Complete genome sequence analysis of a plant growth-promoting phylloplane Bacillus altitudinis FD48 offers mechanistic insights into priming drought stress tolerance in rice

Bacillus altitudinis FD48 is a multifunctional plant growth-promoting bacterium isolated from the phylloplane of rice and survives at --10 bars of osmotic potential (--1.0 MPa). It also serves as an ideal PGPM against drought stress by triggering antioxidant defense mechanisms in rice. To further unravel the genetic determinants of osmotic stress tolerance and plant growth-promoting traits, the whole genome sequence of FD48 was compared with its related strains. The whole genome analysis revealed a single chromosome with a total length of 3,752,533 bp (3.7 Mb) and an average G + C ratio of 41.19%. A total of 4029 genes were predicted, of which 3964 (98.4%) were protein-encoding genes (PEGs) and 65 (1.6%) were non-protein-coding genes. The interaction of FD48 with the host plants is associated with many chemotactic and motility-related genes. The ability of FD48 to colonize plants and maintain plant growth under adverse environmental conditions was evidenced by the presence of genes for plant nutrient acquisition, phytohormone synthesis, trehalose, choline, and glycine betaine biosynthesis, microbial volatile organic compounds (acetoin synthesis), heat and cold shock chaperones, translation elongation factor TU (Ef-Tu), siderophore production, DEAD/DEAH boxes, and non- ribosomal peptide synthase clusters (bacilysin, fengycin, and bacitracin). This study sheds light on the drought stress-resilient mechanism, metabolic pathways and potential activity, and plant growth-promoting traits of B. altitudinis FD48 at the genetic level.

Isolation and identification of marine Bacillus altitudinis KB1 from coastal Kerala: asparaginase producer

L-asparaginase is a target for many researchers as its properties against cancer, especially leukaemia, and protective agents reduce acrylamide in fried food. In this study, the water samples from Thumba Arattuvazhi Beach in Kerala were screened for l-asparaginase producing microorganisms. This was followed by colourimetric screening using modified M9 media with 0.009% Phenol red dye and using l-asparagine as a sole nitrogen source. Then, the Nessler assay was performed to quantify the enzyme. Molecular identification was made by 16SrRNA sequencing and aligned the sequence with GeneBank for phylogenetic tree construction using BLAST. Seawater was serially diluted for 10-1 to 10-6 using nutrient agar plates. A total of 19 bacterial colonies were isolated. The colonies were evaluated to produce l-asparaginase according to the pink zone around the colonies on the modified M9 medium using a red phenol indicator. The KB1 sample was selected for further studies according to plate colour assay. Nessler assay of L-asparaginase quantified as 2.537 IU/ml. Molecular characterisation showed the sequence association with Bacillus altitudinis the sequence submitted in Genebank as B. altitudinis KB1 strain. The l-asparaginase II gene (AnsB) was amplified based on the entire length of the hypothetical protein of annotated genome with accession number CP022319.2. The l-asparaginase activity in this study was 57% higher than the reference organism B. altitudinis BITHSP010. The l-asparaginase producing bacterium B. altitudinis KB1 from a marine source in Kerala can produce asparaginase, which can be utilised for biotechnology applications.

Bacterial endophytes: Molecular interactions with their hosts

Plant growth promotion has been found associated with plants on the surface (epiphytic), inside (endophytic), or close to the plant roots (rhizospheric). Endophytic bacteria mainly have been researched for their beneficial activities in terms of nutrient availability, plant growth hormones, and control of soil-borne and systemic pathogens. Molecular communications leading to these interactions between plants and endophytic bacteria are now being unrevealed using multidisciplinary approaches with advanced techniques such as metagenomics, metaproteomics, metatranscriptomics, metaproteogenomic, microRNAs, microarray, chips as well as the comparison of complete genome sequences. More than 400 genes in both the genomes of host plant and bacterial endophyte are up- or downregulated for the establishment of endophytism and plant growth-promoting activity. The involvement of more than 20 genes for endophytism, about 50 genes for direct plant growth promotion, about 25 genes for biocontrol activity, and about 10 genes for mitigation of different stresses has been identified in various bacterial endophytes. This review summarizes the progress that has been made in recent years by these modern techniques and approaches.