Biology subjects

Gastelum, G.

Publications and source records attributed to Gastelum, G..

3 recordsLinked to original sources

bioRxiv2024

Harnessing Emergent Properties of Microbial Consortia: Assembly of the Xilonen SynCom

Synthetic communities (SynComs) are valuable tools for addressing fundamental questions in microbial ecology regarding community assembly. They could also potentially aid in successfully manipulating microbial communities for clinical, biotechnological, and agricultural applications. SynCom design is complicated since interactions between microbes cannot be predicted based on their individual properties. Here, we aimed to assemble a higher-order SynCom from seed-endophytic bacteria isolated from native maize landraces. We screened co-cultures that included strains from the Bacilli class, and the Burkholderia and Pseudomonas genera since these taxa have been previously shown to be important for the fertility of native maize landraces. We developed a combinatorial, bottom-up strategy aimed at the detection of a complex colony architecture as an emergent collective property. Using this simplified approach, we assembled a SynCom composed of Bacillus pumilus NME155, Burkholderia contaminans XM7 and Pseudomonas sp. GW6. The strains exhibited positive and negative interactions when evaluated in pairs, but their higher-order assembly results in a complex colony architecture, which is considered a proxy of biofilm formation. This SynCom was named Xilonen after the Aztec goddess of young maize and fertility. The Xilonen SynCom will aid in studying the molecular and ecological basis mediating maize fertility.

microbiology↗

bioRxiv2024

Biofilm formation and maize root-colonization of seed-endophytic Bacilli isolated from native maize landraces

Agricultural microbiology seeks to replace the use of agrochemicals with microbe-based products. Plant growth-promoting bacteria (PGPB) are often selected based on their functions in vitro, and then, their effect on plant development is tested. However, this approach neglects the study of their survival in soil, root-colonization, and the monitoring of beneficial functions in the rhizosphere. This could explain the recurrent lack of success in the transition from lab tests to field applications of natural isolates from novel habitats. In our recent studies, we found that native maize seeds from traditional agroecosystems carry endophytic bacterial communities that are dominated by members of the class Bacilli. As an approach to grasp their PGP potential, we developed protocols to test maize root-colonization of these natural isolates in 1) a short-term hydroponics assay in vitro and 2) a long-term assay in non-sterile soil pots. Our results show that in vitro biofilm formation was only partially associated to short-term colonization in vitro; furthermore, long-term root-colonization in soil pots was not correlated to the in vitro assays. This work highlights the necessity to incorporate root-colonization assays as part of the research strategies in the search for PGPB natural isolates from unexplored habitats, towards the generation of inoculants with increased success in the field.

microbiology↗

bioRxiv2019

Rap-protein paralogs of B. thuringiensis: a multifunctional and redundant regulatory repertoire for the control of collective functions.

Quorum Sensing (QS) are mechanisms of synthesis and detection of signaling molecules to regulate gene expression and coordinate behaviors in bacterial populations. In Bacillus subtilis (Bs), multiple paralog Rap-Phr QS systems (receptor-signaling peptide) are highly redundant and multifunctional, interconnecting the regulation of differentiation processes such as sporulation and competence. However, their functions in the B. cereus group are largely unknown. We evaluated the diversification of Rap-Phr systems in the B. cereus group as well as their functions, using Bacillus thuringiensis Bt8741 as model. Bt8741 codes for eight Rap-Phr systems; these were overexpressed to study their participation in sporulation, biofilm formation, extracellular proteolytic activity and spreading. Our results show that five Rap-Phr systems (RapC, K, F, I and RapLike) inhibit sporulation, two of which (RapK and RapF) probably dephosphorylate of Spo0F from the Spo0A phosphorelay; these two Rap proteins also inhibit biofilm formation. Five systems (RapC, F, F2, I1 and RapLike) decrease extracellular proteolytic activity; finally, four systems (RapC, F1, F2 and RapLike) participate in spreading inhibition. Our bioinformatic analyses showed that Rap proteins from the B. cereus group diversified into five pherogroups, and we foresee that functions performed by Rap proteins of Bt8741 could also be carried out by Rap homologs in other species within the group. These results indicate that Rap-Phr systems constitute a highly multifunctional and redundant regulatory repertoire that enables bacteria from the B. cereus group to efficiently regulate collective functions during the bacterial life cycle, in the face of changing environments.\n\nImportanceThe Bacillus cereus group of bacteria includes species of high economic, clinical, biological warfare and biotechnological interest, e.g. B. anthracis in bioterrorism, B. cereus in food intoxications and B. thuringiensis in biocontrol. Knowledge on the ecology of these bacteria is hindered due to our limited understanding about the regulatory circuits that control differentiation and specialization processes. Here, we uncover the participation of eight Rap quorum-sensing receptors in collective functions of B. thuringiensis. These proteins are highly multifunctional and redundant in their functions, linking ecologically relevant processes such as sporulation, biofilm formation, extracellular proteolytic activity, spreading, and probably other additional functions in species from the B. cereus group.

microbiology↗