Biology subjects

Garcia-Maldonado, J. Q.

Publications and source records attributed to Garcia-Maldonado, J. Q..

4 recordsLinked to original sources

bioRxiv2026

Within-colony microbial response of three species with different susceptibility to Stony Coral Tissue Loss Disease

Stony coral tissue loss disease (SCTLD), a coral pathology with rapid tissue loss and high mortality rate has affected nearly 30 species with a variable degree of susceptibility across species. It has been suggested that SCTLD has a systemic effect within coral colonies, but little is known about within-colony changes of the microbial communities associated with this disease. Here we evaluate the microbial shifts within coral colonies: apparently healthy tissue and SCTLD tissue. The study was done in three species following a gradient of susceptibility to the disease: Dendrogyra cylindrus (Dcyl, n = 11) and Pseudodiploria strigosa (Pstr, n = 6) two highly susceptible species; and Orbicella faveolata (Ofav, n = 8), a moderately affected species. 16S rRNA Illumina sequences analysis showed differential microbial community structure within two species (Dcyl, p = 0.01, Pstr, p = 0.01) but not for Ofav (p = 0.28). Taxonomic profiles of bacterial groups were species-specific in SCTLD tissue, but healthy tissue shared similarities between species including Pirelullales, NB1-J and SAR324. Our results reveal that the microbial communities effects associated to the disease follow a similar pattern to the species susceptibility to SCTLD, providing new insights into the disease dynamics in the Mexican Caribbean.

microbiology↗

bioRxiv2026

A microbiome assessment of healthy and bleached Halymenia floresii (Clemente) C. Agardh (Rhodophyta, Florideophyceae)

Macroalgae serve as critical habitat-formers and primary producers in coastal ecosystems, functioning across near-subtidal and intertidal zones in three distinct states: substrate-attached, free-floating (drift), and beach-cast. While substrate-attached macroalgae are susceptible to infectious diseases with significant ecological implications, diseases affecting drift macroalgal communities remain virtually unstudied. Here, we investigated bleaching disease - one of the most common macroalgal afflictions - in the drift rhodophyte Halymenia floresii from the Gulf of Mexico. Using 16S rRNA gene high-throughput sequencing and scanning electron microscopy, we characterized the bacterial community structure and composition associated with the free-floating healthy, bleached and degrading H. floresii to understand how bacterial partners respond to host health status. Principal Coordinate Analysis based on UniFrac distance revealed distinct clustering of bacterial communities according to host health condition. Shannon diversity indices showed distinct patterns ranging from 1.14 - 3.15 for healthy, bleached, and degrading samples, while Simpson indices ranged from 0.62 to 0.91, reflecting substantial variation in community evenness. In healthy samples, Cyanobacteria (17 - 52%) and Pseudomonadota (previously, Proteobacteria) (41 - 81%) dominated, and the bleached samples were characterized by elevated Bacteroidota (formerly, Bacteroidetes) (5 - 35%) and Pseudomonadota (41 - 88%). Notably, Novosphingobium (25 - 49%) dominated healthy hosts while showing lower abundance in degrading (13 - 17%) and bleached (18 - 22%) specimens. Conversely, Reinekea emerged as a dominant genus (22.5%) specifically in bleached samples, suggesting a potential role in disease pathogenesis. Microbial network analysis using NetCoMi revealed three distinct bacterial clusters corresponding to health states: a healthy-associated cluster dominated by Novosphingobium and uncultured Cyanobacterial with predominantly positive associations, and two disease-associated clusters enriched in opportunistic genera including Reinekea, Vibrio, Colwellia, and Alteromonas, indicating network reorganization from cooperative to exploitative interactions. This study provides the first descriptive assessment of microbiome transitions associated with bleaching disease in a drift macroalga and highlights the importance of considering free-floating macroalgal diseases and their potential impacts on coastal ecosystem health.

microbiology↗

bioRxiv2024

Microbiomes of three coral species in the Mexican Caribbean and their shifts associated with the Stony Coral Tissue Loss Disease

Stony Coral Tissue Loss Disease (SCTLD) has caused widespread coral mortality in the Caribbean Region. However, how the disease presence alters the microbiome community, their structure, composition, and metabolic functionality is still poorly understood. In this study, we characterized the microbial communities of the tissues of apparently healthy and diseased SCTLD colonies of the species Siderastrea siderea, Orbicella faveolata, and Montastraea cavernosa to explore putative changes related to the presence of SCTLD. Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia were the best represented classes in the healthy tissues of all coral species, and alpha diversity did not show significant differences among the species. The microbial community structure between coral species was significantly different (PERMANOVA: F=3.46, p=0.001), and enriched genera were detected for each species: Vibrio and Photobacterium in S. siderea, Spirochaeta2 and Marivivens in O. faveolata and SAR202_clade and Nitrospira in M. cavernosa. Evidence of SCTLD in the microbial communities was more substantial in S. siderea, where differences in alpha diversity, beta diversity, and functional profiles were observed. In O. faveolata, differences were detected only in the community structure, while M. cavernosa samples showed no significant difference. Several microbial groups were found to have enriched abundances in tissue from SCTLD lesions from S. siderea and O. faveolata, but no dominant bacterial group was detected. Our results contribute to understanding microbial diversity associated with three scleractinian coral species and the shifts in their microbiomes associated with SCTLD in the Mexican Caribbean.

microbiology↗

bioRxiv2024

Highly diverse - low abundance methanogenic communities in hypersaline microbial mats of Guerrero Negro B.C.S., assessed through microcosm experiments

Methanogenic communities of hypersaline microbial mats of Guerrero Negro, Baja California Sur, Mexico, have been recognized to be dominated by methylotrophic methanogens. However, recent studies of environmental samples have evidenced the presence of hydrogenotrophic and methyl-reducing methanogenic members, although at low relative abundances. Physical and geochemical conditions that stimulate the development of these groups in hypersaline environments, remains elusive. Thus, in this study the taxonomic diversity of methanogenic archaea of two sites of Exportadora de Sal S.A was assessed by mcrA gene high throughput sequencing from microcosm experiments with different substrates (both competitive and non-competitive). Results confirmed the dominance of the order Methanosarcinales in all treatments, but an increase in the abundance of Methanomassiliiccocales was also observed, mainly in the treatment without substrate addition. Moreover, incubations supplemented with hydrogen and carbon dioxide, as well as the mixture of hydrogen, carbon dioxide and trimethylamine, managed to stimulate the richness and abundance of other than Methanosarcinales methanogenic archaea. Several OTUs that were not assigned to known methanogens resulted phylogenetically distributed into at least nine orders. Environmental samples revealed a wide diversity of methanogenic archaea of low relative abundance that had not been previously reported for this environment, suggesting that the importance and diversity of methanogens in hypersaline ecosystems may have been overlooked. This work also provided insights into how different taxonomic groups responded to the evaluated incubation conditions.

microbiology↗