Biology subjects

Olivares, F. L.

Publications and source records attributed to Olivares, F. L..

9 recordsLinked to original sources

bioRxiv2025

Genomic plasticity of the Azospirillum genus in a biotechnological context

Extensive agriculture and the use of chemical fertilizers cause notable environmental impacts on multiple levels, from reducing soil microbiota diversity to groundwater contamination. In this context, the usage of plant growth-promoting bacteria (PGPB) presents a sustainable alternative to enhance crop production while mitigating these adverse effects. Azospirillum, a bacterial genus renowned for its beneficial capabilities, particularly phytohormone production, is a key component of many commercial inoculants. In this work, we performed a comparative genomic analysis of all publicly available Azospirillum genomes and four novel isolates belonging to our microbial collection. Our analysis identified a species complex within the genus, which we designate the A. brasilense species complex, comprising species already used in commercial bioconsortia. This complex is characterized by a core set of exclusive genes linked to chemotaxis and host-recognition capability. Furthermore, we also validated the biosafety of the A. brasilense species complex and confirmed the plant growth-promoting potential of our novel isolates, highlighting their suitability for developing new biofertilizers.

microbiology↗

bioRxiv2024

Comparative metagenomic profiling of seed-borne microbiomes in a landrace and a hybrid maize variety

The plant seed-borne microbiome comprises microorganisms vertically inherited from the mother plant. This microbiome is often linked to early-life protection and seedling growth promotion. Here, we compare the seed-borne bacteriomes of a commercial hybrid and a landrace maize variety. The landrace variety displays a more diverse seed-borne microbiome, featuring a variety of taxa across samples. In contrast, the microbiome of the hybrid variety is less diverse and more uniform across samples. Although both microbiomes lack a functional nitrogen fixation apparatus, we found a remarkably distinct presence of genes associated with phytohormone production and phosphate solubilization, particularly in the landrace variety. In addition, we recovered 18 metagenome-assembled genomes (MAGs), including four from potentially novel species. Collectively, our results allow a better understanding of the contrasting diversity between maize varieties and open important perspectives for designing synthetic microbial communities for agroecosystems.

plant biology↗

bioRxiv2021

Genome sequencing of the vermicompost strain Stenotrophomonas maltophilia UENF-4GII and population structure analysis of the S. maltophilia Sm3 genogroup

The Stenotrophomonas maltophilia complex (Smc) is a cosmopolitan bacterial group that has been proposed an emergent multidrug-resistant pathogen. Taxonomic studies support the genomic heterogeneity of Smc, which comprises genogroups exhibiting a range of phenotypically distinct strains from different sources. Here, we report the genome sequencing and in-depth analysis of S. maltophilia UENF-4GII, isolated from vermicompost. This genome harbors a unique region encoding a penicillin-binding protein (pbpX) that was carried by a transposon, as well as horizontally-transferred genomic islands involved in anti-phage defense via DNA modification, and pili glycosylation. We also analyzed all available Smc genomes to investigate genes associated with resistance and virulence, niche occupation, and population structure. S. maltophilia UENF-4GII belongs to genogroup 3 (Sm3), which comprises three phylogenetic clusters (PC). Pan-GWAS analysis uncovered 471 environment-associated and 791 PC-associated genes, including antimicrobial resistance (e.g. blaL1 and blaR1) and virulence determinants (e.g. treS and katG) that provide insights on the resistance and virulence potential of Sm3 strains. Together, the results presented here provide the grounds for more detailed clinical and ecological investigations of S. maltophilia.

microbiology↗

bioRxiv2021

Characterization of cellular, biochemical and genomic features of the diazotrophic plant growth-promoting bacterium Azospirillum sp. UENF-412522, a novel member of the Azospirillum genus

Given their remarkable beneficial effects on plant growth, several Azospirillum isolates currently integrate the formulations of various commercial inoculants. Our research group isolated a new strain, Azospirillum sp. UENF-412522, from passion fruit rhizoplane. This isolate uses carbon sources that are partially distinct from closely-related Azospirillum isolates. Scanning electron microscopy analysis and population counts demonstrate the ability of Azospirillum sp. UENF-412522 to colonize the surface of passion fruit roots. In vitro assays demonstrate the ability of Azospirillum sp. UENF-412522 to fix atmospheric nitrogen, to solubilize phosphate and to produce indole-acetic acid. Passion fruit plantlets inoculated with Azospirillum sp. UENF-41255 showed increased shoot and root fresh matter, as well as root dry matter, further highlighting its biotechnological potential for agriculture. We sequenced the genome of Azospirillum sp. UENF-412522 to investigate the genetic basis of its plant-growth promotion properties. We identified the key nif genes for nitrogen fixation, the complete PQQ operon for phosphate solubilization, the acdS gene that alleviates ethylene effects on plant growth, and the napCAB operon, which produces nitrite under anoxic conditions. We also found several genes conferring resistance to common soil antibiotics, which are critical for Azospirillum sp. UENF-412522 survival in the rhizosphere. Finally, we also assessed the Azospirillum pangenome and highlighted key genes involved in plant growth promotion. A phylogenetic reconstruction of the genus was also conducted. Our results support Azospirillum sp. UENF-412522 as a good candidate for bioinoculant formulations focused on plant growth promotion in sustainable systems.

microbiology↗

bioRxiv2020

Mutualistic interaction with Trichoderma longibrachiatum UENF-F476 boosted plant growth-promotion of Serratia marcescens UENF-22GI

BACKGROUNDA plethora of bacteria-fungal interactions occurs on the extended fungal hyphae network in soil. The mycosphere of saprophytic fungi can serve as a bacterial niche boosting their survival, dispersion, and activity. Such ecological concepts can be converted to bioproducts for sustainable agriculture. Accordingly, we tested the hypothesis that the well-characterized beneficial bacterium Serratia marcescens UENF-22GI can enhance their plant growth-promoting properties by combination with Trichoderma longibrachiatum UENF-F476. RESULTSThe colony and cell interactions demonstrated S. marcescens and T. longibrachiatum compatibility. Bacteria cells were able to attach, forming aggregates-biofilms and migrates through fungal hyphae network. Bacterial migration through growing hyphae was confirmed using two-compartment Petri dishes assay. Fungal inoculation increased the bacteria survival rates into the vermicompost substrate over the experimental time. Also, in vitro indolic compound, phosphorus, and zinc solubilization bacteria activities increased in the presence of the fungus. In line with the ecophysiological bacteria fitness, tomato and papaya plantlet growth was boosted by bacteria-fungi combination applied under plant nursery conditions. CONCLUSIONMutualistic interaction between mycosphere-colonizing bacterium S. marcescens UENF-22GI and the saprotrophic fungi T. longibrachiatum UENF-F467 increased the ecological fitness of the bacteria alongside with beneficial potential for plant growth. A proper combination and delivery of compatible beneficial bacteria-fungus represent an open avenue for biological enrichment of plant substrates technologies in agricultural systems.

microbiology↗

bioRxiv2020

Altered bacteria community dominance reduces tolerance to resident fungus and seed to seedling growth performance in maize (Zea mays L. var. DBK 177).

Seeds are reservoirs of beneficial and harmful microorganism that modulates plant growth and health. Here, we access seed to seedling bacteriome assembly modified by seed-disinfection and the underlined effect over maize germination performance and root-seedlings microbial colonization. Seed-disinfection was performed with sodium hypochlorite (1.25%, 30 min), resulting in a reduction of the cultivable-dependent fraction of seed-borne bacteria population, but not significantly detected by real-time PCR, microscopy, and biochemical analysis of the roots on germinated seeds. 16S rRNA sequencing revealed that the seed and root bacteriome exhibited similar diversity and did not differ in the structure concerning seed-disinfection. On the other hand, the abundance reduction of the genera f_Enterobacteriaceae_922761 (unassigned genus), Azospirillum, and Acinetobacter in disinfected-seed prior germination seems to display changes in prominence of several new taxa in the roots of germinated seeds. Interestingly, this reduction in the bacteriome negatively affected the germination speed and growth of maize plantlets. Additionally, bacteriome re-shape increased the maize var DKB 177 susceptible to the seed-borne plant pathogen Penicillium sp. Such changes in the natural seed-borne composition removed the natural barrier, increasing susceptibility to pathogens, impairing disinfected seeds to germinate, and develop. We conclude that bacteria borne in seeds modulate the relative abundance of taxa in the root, promote germination, seedling growth, and protect the maize against fungal pathogens.

microbiology↗

bioRxiv2020

Insights into the structure and role of seed-borne bacteriome during maize germination

Seed germination events modulate microbial community composition, which ultimately influences seed to seedling growth performance. Here we assess the seed-borne bacteria community in disinfected and non-disinfected maize seeds and seedlings. Using a gnotobiotic system, sodium hypochlorite (1.25%, 30 min) treated-seeds showed a reduction of bacteria population size and an increase of bacteria community diversity associated with selective suppression of Burkholderia related taxon. The shift in the bacteria community composition in disinfested-seeds negatively affects germination speed, seedling growth, and reserve mobilization rates in comparison with non-disinfected maize seeds. A synthetic bacteria community formed by twelve isolates (9 Burkholderia spp.; 2 Bacillus spp. and 1 Staphylococcus sp.) obtained from natural microbiota of maize seeds herein were capable of recovering germination and seedling growth when reintroduced in disinfected seeds. 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 taxon 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. One sentence summarypartial removal of the seed-borne microbiota negatively affects maize seedling growth performance and altered bacteria community structure. Partial microbial recomposition, mainly with Burkholderia-related isolates, restores the germination phenotype of disinfested seeds.

microbiology↗

bioRxiv2019

Population structure and pangenome analysis of Enterobacter bugandensis uncover the presence of blaCTX-M-55, blaNDM-5 and blaIMI-1, along with sophisticated iron acquisition strategies

Enterobacter bugandensis is a recently described species that has been largely associated with nosocomial infections. Here, we report the genome of a non-clinical E. bugandensis strain. We used this and other several publicly available E. bugandensis genomes to obtain the species pangenome, investigate the conservation of important genes, and elucidate general population structure features of the species. Core- and whole-genome multilocus sequence typing (cgMLST and wgMLST, respectively) allowed the detection of five E. bugandensis phylogroups (PG-A to E). We found important antimicrobial resistance and virulence determinants associated with specific PGs, notably PG-A and PG-E. IncFII was the most prevalent plasmid replicon type in this species. We uncovered several extended-spectrum {beta}-lactamases, including blaCTX-M-55 and blaNDM-5, present in an IncX replicon type plasmid, described here for the first time in E. bugandensis. Genetic context analysis of blaNDM-5 revealed the resemblance of this plasmid with other IncX plasmids isolated from other bacteria from the same country. Further, three distinctive siderophore producing operons were found in the E. bugandensis pangenome: enterobactin (ent), aerobactin (iuc/iut), and salmochelin (iro). The latter operon is conserved in all PG-E isolates. Collectively, our findings provide novel insights on the lifestyle, physiology, antimicrobial, and virulence profiles of E. bugandensis.

genomics↗

bioRxiv2018

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

Plant-bacteria associations have been extensively studied for their potential in increasing crop productivity in a sustainable manner. Serratia marcescens is a Gram-negative species found in a wide range of environments, including soil. Here we describe the genome sequencing and assessment of plant-growth promoting abilities of S. marcescens UENF-22GI (SMU), a strain isolated from mature cattle manure vermicompost. In vitro, SMU 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 SMU remarkably increased seedling growth and biomass under greenhouse conditions. The SMU genome has 5 Mb, assembled in 17 scaffolds comprising 4,662 genes (4,528 are protein-coding). No plasmids were identified. SMU is phylogenetically placed within a clade comprised almost exclusively of environmental strains. We were able to find the genes and operons that are likely responsible for all the interesting plant-growth promoting features that were experimentally described. Genes involved other interesting properties that were not experimentally tested (e.g. tolerance against metal contamination) were also identified. The SMU 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 the SMU competitiveness against other bacteria. 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.

microbiology↗