Genome sequencing and assessment of plant growth-promoting properties of a Serratia marcescens strain isolated from vermicompost.

BACKGROUND: Plant-bacteria associations have been extensively studied for their potential in increasing crop productivity in a sustainable manner. Serratia marcescens is a species of Enterobacteriaceae found in a wide range of environments, including soil. RESULTS: Here we describe the genome sequencing and assessment of plant growth-promoting abilities of S. marcescens UENF-22GI, a strain isolated from mature cattle manure vermicompost. In vitro, S. marcescens UENF-22GI is able to solubilize P and Zn, to produce indole compounds (likely IAA), to colonize hyphae and counter the growth of two phytopathogenic fungi. Inoculation of maize with this strain remarkably increased seedling growth and biomass under greenhouse conditions. The S. marcescens UENF-22GI genome has 5 Mb, assembled in 17 scaffolds comprising 4662 genes (4528 are protein-coding). No plasmids were identified. S. marcescens UENF-22GI is phylogenetically placed within a clade comprised almost exclusively of non-clinical strains. We identified genes and operons that are likely responsible for the interesting plant-growth promoting features that were experimentally described. The S. marcescens UENF-22GI genome harbors a horizontally-transferred genomic island involved in antibiotic production, antibiotic resistance, and anti-phage defense via a novel ADP-ribosyltransferase-like protein and possible modification of DNA by a deazapurine base, which likely contributes to its competitiveness against other bacteria. CONCLUSIONS: Collectively, our results suggest that S. marcescens UENF-22GI is a strong candidate to be used in the enrichment of substrates for plant growth promotion or as part of bioinoculants for agriculture.

Serine proteases activity is important for the interaction of nematophagous fungus Duddingtonia flagrans with infective larvae of trichostrongylides and free-living nematodes Panagrellus spp.

The nematode-trapping fungus Duddingtonia flagrans has been studied as a possible control method for gastrointestinal nematodes of livestock animals. These fungi capture and infect the nematode by cuticle penetration, immobilization, and digestion of the internal contents. It has been suggested that this sequence of events occurs by a combination of physical and enzymatical activities. The aim of this study was to investigate the participation of proteolytic enzymatic activity during the interaction of the nematophagous fungus D. flagrans with infective larvae of trichostrongylides and the free-living nematode Panagrellus spp. Protease inhibitors used interfered in the predatory activity of D. flagrans. However, only PMSF significantly reduced the mean number of Panagrellus spp. captured by D. flagrans in comparison with the control. The experiment with fluorogenic substrate showed that maximum urokinase activity during the interaction of the fungus with the infective larvae of trichostrongylides or Panagrellus spp. occurred within 7 or 1 h of incubation, respectively. The protease activity, especially of the serine class, may be important during the interaction between the fungus and nematodes.