Bacillus velezensis FZB42 in 2018: The Gram-Positive Model Strain for Plant Growth Promotion and Biocontrol

Abstract

Bacillus velezensis FZB42, the model strain for Gram-positive plant-growth-promoting and biocontrol rhizobacteria, has been isolated in 1998 and sequenced in 2007. In order to celebrate these anniversaries, we summarize here the recent knowledge about FZB42. In last 20 years, more than 140 articles devoted to FZB42 have been published. At first, research was mainly focused on antimicrobial compounds, apparently responsible for biocontrol effects against plant pathogens, recent research is increasingly directed to expression of genes involved in bacteria-plant interaction, regulatory small RNAs (sRNAs), and on modification of enzymes involved in synthesis of antimicrobial compounds by processes such as acetylation and malonylation. Till now, 13 gene clusters involved in non-ribosomal and ribosomal synthesis of secondary metabolites with putative antimicrobial action have been identified within the genome of FZB42. These gene clusters cover around 10% of the whole genome. Antimicrobial compounds suppress not only growth of plant pathogenic bacteria and fungi, but could also stimulate induced systemic resistance (ISR) in plants. It has been found that besides secondary metabolites also volatile organic compounds are involved in the biocontrol effect exerted by FZB42 under biotic (plant pathogens) and abiotic stress conditions. In order to facilitate easy access to the genomic data, we have established an integrating data bank 'AmyloWiki' containing accumulated information about the genes present in FZB42, available mutant strains, and other aspects of FZB42 research, which is structured similar as the famous SubtiWiki data bank.

Keywords: AmyloWiki; Bacillus velezensis; FZB42; induced systemic resistance (ISR); non-ribosomal synthesized lipopeptides (NRPS); non-ribosomal synthesized polyketides (PKS); plant growth promoting bacteria (PGPR); volatiles.

FIGURE 1

NJ phylogenomic tree, constructed from 11 type strain genomes with highest similarity to B. subtilis 168^T. The genome of B. licheniformis DSM13 was used as outgroup. The tree was build out of a core of 1946 genes per genome, 21406 in total. The core has 586283 AA-residues/bp per genome, 6449113 in total. B. velezensis FZB42 (labeled in red) is a member of the operational group B. amyloliquefaciens (boxed). The scale bar corresponds to 0.01 substitutions per site.

FIGURE 2

The Venn diagram of Bacillus amyloliquefaciens DSM7 (1), Bacillus velezensis FZB42 (2), and Bacillus subtilis subtilis 168 (3). The numbers of reciprocal best hits between subsets of genomes are shown. Note, 100% identical paralogous genes were not counted in the Venn diagram numbers (Blom et al., 2016). The three strains share 3050 genes according to the best hit calculation, whilst 268 genes were found unique in FZB42. A direct comparison between FZB42 and B. subtilis 168 revealed that they have 3122 genes in common, whilst 522 genes were found unique in FZB42.

FIGURE 3

Distribution of FZB42 malonylated proteins in various functional categories according to the GO database. The ratio of Kmal sites located in the protein to all KmaI sites was compared with the ratio of malonylated proteins to all proteins in the database. The one-tailed Fisher’s exact test was used to test the enrichment and the result with p-value < 0.05 is considered significant.

FIGURE 4

Home page of AmyloWiki, an integrated data base of FZB42.