Biology subjects

Santoyo, G.

Publications and source records attributed to Santoyo, G..

5 recordsLinked to original sources

bioRxiv2026

Unravelling genomic and functional traits of two biocontrol and plant growth-promoting Pseudomonas endophytes

Plant growth-promoting bacterial endophytes represent a sustainable strategy for enhancing agricultural productivity while reducing reliance on synthetic fertilizers and pesticides. This study focused on the genomic and functional characterization of two endophytic bacterial strains, R11F and R19M, isolated from bean and maize roots, respectively. Comparative analyses based on 16S rRNA gene sequences, average nucleotide identity (ANI), and genome-to-genome distance calculations (GGDC) classified both isolates as Pseudomonas palleroniana. Comparative genomic analyses revealed highly conserved genomes containing genes associated with plant colonization, phosphate solubilization, stress adaptation, heavy metal resistance, and hydrocarbon degradation. Genome mining further identified 17 and 18 biosynthetic gene clusters (BGCs) in R11F and R19M, respectively, including non-ribosomal peptide synthetases (NRPS), pyoverdine, NRP-metallophores, RiPP-like compounds, arylpolyenes, {beta}-lactones, terpenes, NAGGN, and hydrogen cyanide. Strain-specific BGCs associated with syringomycin and viscosin biosynthesis were identified in R11F, whereas R19M harbored clusters related to asplenin and kolossin biosynthesis. In vitro assays confirmed indole production, phosphate solubilization, and siderophore production, as well as the ability of both strains to grow in nitrogen-free medium. Both strains significantly inhibited the growth of Fusarium oxysporum, Phytophthora cinnamomi, and Colletotrichum gloeosporioides. Furthermore, plant inoculation assays demonstrated host-dependent growth promotion, with R11F showing the most consistent improvements in plant growth parameters in tomato, wheat, and lentil. Overall, the integration of comparative genomics and experimental validation demonstrates that P. palleroniana R11F and R19M possess complementary traits associated with plant growth promotion, pathogen suppression, saline stress adaptation, and bioremediation.

microbiology↗

bioRxiv2023

Inoculation with Pseudomonas fluorescens UM270 alters the maize root-associated endobiome and interacting networks in a milpa model

The traditional milpa system is a polyculture originating in Mesoamerica, whose core is maize (Zea mays L.), associated with squash (Cucurbita spp.) and beans (Phaseolus vulgaris L.). In recent years, milpa-type crops have decreased owing to climate change, rapid population growth, and the excessive use of agrochemicals; therefore, the application of plant growth-promoting rhizobacteria (PGPR) to counteract these negative effects has been little explored. In this study, a maize crop in a milpa system was fertilized with the PGPR Pseudomonas fluorescens UM270, and the endophytic root microbiome (endobiome) of maize was assessed by 16S rRNA and internal transcribed spacer regions (ITS) sequencing. The results showed that UM270 the rhizosphere inoculation of P. fluorescens UM270 did not increase alpha diversity in either monoculture or the milpa, but it did alter the endophytic microbiome of maize plant roots by stimulating the presence of bacterial operational taxonomic units (OTUs) of the genera Burkholderia and Pseudomonas (in a monoculture), whereas in the milpa system, the PGPR stimulated a greater endophytic diversity and the presence of genera such as Burkholderia, Variovorax, and N-fixing rhizobia genera, including Rhizobium, Mesorhizobium and Bradyrhizobium. No clear association was found between fungal diversity and the presence of strain UM270, but beneficial fungi such as Rizophagus irregularis and Exophiala pisciphila were detected in the milpa system. In addition, network analysis revealed unique interactions with species like Stenotrophomonas sp., Burkholderia xenovorans, and Sphingobium yanoikuyae, which would potentially be playing a beneficial role with the plant. To the best of our knowledge, this is the first study in which the root microbiome of maize growing under a milpa model was assessed by bio-inoculation with PGPRs.

plant biology↗

bioRxiv2022

Cardiolipin synthesis in Pseudomonas fluorescens UM270 plays a relevant role in stimulating plant growth under salt stress

Membrane cardiolipin (CL) phospholipids play a fundamental role in the adaptation of bacteria to various environmental conditions, including saline stress. Here, we constructed deletion mutants of two CL synthetase genes, clsA and clsB, in the rhizobacterium Pseudomonas fluorescens UM270, and evaluated their role in plant growth promotion under salt stress. P. fluorescens UM270 {Delta}clsA and {Delta}clsB mutants showed a significant reduction in CL synthesis compared to the UM270 wild-type strain (58% {Delta}clsA and 53% {Delta}clsB), and their growth rate was not affected, except when grown at 100 and 200 mM NaCl. Additionally, the root colonization capacity of both mutant strains was impaired compared with that of the wild type. Concomitant with the deletion of clsA and clsB, some physiological changes were observed in the UM270 {Delta}clsA and {Delta}clsB mutants, such as a reduction in indole acetic acid and biofilm production. By contrast, an increase in siderophore biosynthesis was observed. Further, inoculation of the UM270 wild-type strain in tomato plants (Lycopersicon esculentum Saladette) grown under salt stress conditions (100 and 200 mM NaCl) resulted in an increase in root and shoot length, chlorophyll content, and dry weight. On the contrary, when each of the mutants ({Delta}clsA and {Delta}clsB) were inoculated in tomato plants, a reduction in root length was observed when grown at 200 mM NaCl, but the shoot length, chlorophyll content, and total plant dry weight parameters were significantly reduced under normal or saline conditions (100 and 200 mM NaCl), compared to UM270 wild-type-inoculated plants. In conclusion, these results suggest that CL synthesis in P. fluorescens UM270 plays an important role in the promotion of tomato plant growth under normal conditions, but to a greater extent, under salt-stress conditions.

microbiology↗

bioRxiv2022

Genome mining, phylogenetic, and functional analysis of arsenic (As) resistance operons in Bacillus strains, isolated from As-rich hot spring microbial mats

The geothermal zone of Araro, Mexico, is located within the trans-Mexican volcanic belt, an area with numerous arsenic (As)-rich hot springs. In this study, the draft genome sequence of two endemic Bacillus strains (ZAP17 and ZAP62) from Araro microbial mat hot springs was determined, which were able to grow on arsenate (up to 64 mM) and arsenite (up to 32 mM). Phylogenetic analysis based on 16S rRNA and gyrB sequences, as well as genome sequence analysis based on average nucleotide identity (>96%) and digital DNA-DNA hybridization (>70%), indicated that these strains belong to the Bacillus paralicheniformis ZAP17 and Bacillus altitudinis ZAP62. Furthermore, through genome mining, it was identified two arsenic resistance operons, arsRBC, and arsRBCDA in both strains as potential determinants of arsenic (As) resistance. Predicted ArsA (arsenial pump-driving ATPase), ArsB (Arsenical efflux pump protein), ArsC (Arsenate reductase), ArsD (Arsenical efflux pump protein) and ArsR (Metalloregulator/ars operon repressor) proteins, clearly grouped with their respective clades corresponding to other characterized bacterial species, mainly Firmicutes. To further evaluate the functionality of the ars operons in ZAP17 and ZAP62 strains, our results showed that arsRBC and arsRBCDA genes were expressed in the presence of arsenite (III). Finally, the presence of ars operons in the genome of Bacillus species residing in As-rich environments, such as the Araro hot springs, might be a potential mechanism to survive under such harsh conditions, as well as to design sustainable bioremediation strategies.

microbiology↗

bioRxiv2020

Phenotypic plasticity and evolution of thermal tolerance in two lineages of bacteria from temperate and hot environments

Despite the crucial role of microorganisms to sustain life on Earth, there is little research on the evolution of thermal tolerance of bacteria in the face of the challenge that global warming poses. Phenotypic adaptation to a new environment requires plasticity to allow individuals to respond to selective forces, followed by adaptive evolution. We do not know to what extent phenotypic plasticity allows thermal tolerance evolution in bacteria at the border of their physiological limits. We analyzed growth and thermal reaction norms to temperature of strains of two bacterial lineages, Bacillus cereus sensu lato and Bacillus subtilis sensu lato, that evolved in two contrasting environments, a temperate lagoon (T) and a hot spring (H). Our results showed that despite co-occurrence of members of both lineages in the two contrasting environments, norms of reactions to temperature exhibited a similar pattern only within the lineages, suggesting fixed phenotypic plasticity. Additionally, within the B. cereus lineage, strains from the H environment showed only two to three {degrees}C more heat tolerance than strains from the T environment. The limited evolutionary changes towards an increase in heat tolerance in bacteria should alert us of the negative impact that climate change can have on all biological cycles in the planet.

evolutionary biology↗