BackgroundPlant-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.ResultsHere 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.ConclusionsCollectively, 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.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5130-y) contains supplementary material, which is available to authorized users.

No abstract

This study aimed to evaluate the anthelmintic activity of Eucalyptus citriodora essential oil and citronellal on sheep gastrointestinal nematodes. Essential oil composition was determined by gas chromatography mass spectrometry. The substances were evaluated in vitro using adult worm motility test (AWMT) and transmission electron microscopy (TEM). The acute toxicity test in mice and the fecal egg count reduction test (FECRT) in sheep were performed. Citronellal was confirmed as the essential oil major constituent (63.9%). According to the AWMT, 2 mg/mL of essential oil and citronellal completely inhibited Haemonchus contortus motility at 6 h post exposure. H. contortus exposed to essential oil and citronellal exhibited internal ultrastructural modifications. The lethal dose 50 values in mice were 5,000 and 2,609 mg/kg for essential oil and citronellal, respectively. E. citriodora essential oil reduced sheep epg at 14 days post treatment by 69.5% (P<0.05). No significant differences were observed in epg between the citronellal and negative control groups (P>0.05). The interaction between citronellal and other constituents in the essential oil may be relevant for its in vivo anthelmintic activity. Thus, E. citriodora essential oil and citronellal pharmacokinetic studies may help elucidate the anthelmintic activity of these compounds.

Seed germination events modulate microbial community composition, which ultimately influences seed to seedling growth performance. Here we evaluate the germinated maize (variety SHS 5050) root bacterial community of disinfected seed (DS) and non-disinfected seed (NDS). Using a gnotobiotic system, sodium hypochlorite (1.25%, 30 min) treated seeds showed a reduction of bacterial population size and an apparent increase of bacterial community diversity associated with a significant selective reduction of Burkholderia related sequences. The shift in the bacterial community composition in DS negatively affects germination speed, seedling growth, and reserve mobilization rates compared with NDS. A synthetic bacterial community (syncom) formed by twelve isolates (9 Burkholderia spp.; 2 Bacillus spp. and 1 Staphylococcus sp.) obtained from natural microbiota maize seeds herein were capable of recovering germination and seedling growth when reintroduced in DS. Overall results showed that changes in bacterial community composition and selective reduction of Burkholderia related members dominance interfere with germination events and initial growth of the maize plantlets. By cultivation-dependent and independent approaches, we deciphered seed-maize microbiome structure, bacterial niches location, and bacterial taxa with relevant roles in seedlings growth performance. A causal relationship between seed microbial community succession and germination performance open opportunities in seed technologies to build-up microbial communities to boost plant growth and health.

No abstract