Research Outputs
Occurrence of bacteria potentially pathogenic to humans in a harvested intertidal sea snail
Microbes associated with marine invertebrates play a key role in the physiological and biochemical processes of the host, and can be responsible for food-borne diseases in humans. Raw invertebrates are a common component of coastal gastronomy worldwide and their consumption could represent a potential risk to humans if their microbiome hosts infectious bacteria. However, these species’ microbiome composition is usually unknown. In this study, we sequenced the 16S gene to characterise the microbiome of the digestive system and gonads of the commercially-exploited sea snail Phorcus sauciatus from the Macaronesian islands and mainland Portugal. The goal was to identify bacteria that might pose a threat to humans. In total, 910 OTUs were identified, thirty-two of which were found to be classified as Risk level-1 and -2 species. Among these, twenty pathogenic bacterial strains were found in high relative abundance and identified as potential drivers of human diseases, including Micrococcus luteus and Serratia marcescens. Here, we discuss how our findings on the occurrence of these bacteria could seriously affect humans. Our results are relevant beyond the scope of this study, as this work might also pave the way for uncovering further implications on the raw consumption of other shellfish and invertebrate species.
Major ocean currents may shape the microbiome of the topshell Phorcus sauciatus in the NE Atlantic Ocean
Studies on microbial communities are pivotal to understand the role and the evolutionary paths of the host and their associated microorganisms in the ecosystems. Meta-genomics techniques have proven to be one of the most effective tools in the identification of endosymbiotic communities of host species. The microbiome of the highly exploited topshell Phorcus sauciatus was characterized in the Northeastern Atlantic (Portugal, Madeira, Selvagens, Canaries and Azores). Alpha diversity analysis based on observed OTUs showed significant differences among regions. The Principal Coordinates Analysis of beta-diversity based on presence/absence showed three well differentiated groups, one from Azores, a second from Madeira and the third one for mainland Portugal, Selvagens and the Canaries. The microbiome results may be mainly explained by large-scale oceanographic processes of the study region, i.e., the North Atlantic Subtropical Gyre, and specifically by the Canary Current. Our results suggest the feasibility of microbiome as a model study to unravel biogeographic and evolutionary processes in marine species with high dispersive potential.
Pleistocene expansion, anthropogenic pressure and ocean currents: Disentangling the past and ongoing evolutionary history of Patella aspera Röding, 1798 in the archipelago of Madeira
Aims Rising sea-level following the Last Glacial Maximum lead to fragmentation of coastal limpet populations between islands of the Archipelago of Madeira. This fragmentation is reinforced by recent heavy exploitation reducing effective population size on Madeira Island. We use the limpet P. aspera to understand how the role of processes at different time scales (i.e. changes in the sea level and overexploitation) can influence the genetic composition of an extant species, relating these processes to reproductive phenology and seasonal shifts in ocean currents. Location Madeira Island, Porto Santo and Desertas (Archipelago of Madeira, NE Atlantic Ocean). Taxon The limpet Patella aspera. Methods Twelve microsatellite genetic markers were used. A power analysis was used to evaluate the power of the microsatellite markers to detect a signal of population differentiation. Long-term past migrations were assessed using a Bayesian Markov Montecarlo approach in the software MIGRATE-n to estimate mutation-scaled migration rates (M = m/μ; m, probability of a lineage immigrating per generation; μ, mutation rate). Two scenarios were evaluated using an Approximate Bayesian Computation (ABC) in the software DIYABC 2.1 (i) Scenario 1: considered a population scenario from a reduced Ne at time t3 to a higher Ne at time t2; and (ii) Scenario 2 considering a reduction of Ne from a time t3 to a time t2. Results Colonization of the archipelago by Portuguese settlers six centuries ago probably led to an important decrease in the genetic diversity of the species (Ne). Contemporary gene flow strongly support a pattern of high asymmetric connectivity explained by the reproductive phenology of the species and spatio-temporal seasonal changes in the ocean currents. Spatio-temporal reconstructions using Bayesian methods, including coalescent and Approximate Bayesian Computation (ABC) approaches, suggest changes in the migration patterns from highly symmetric to highly asymmetric connectivity with subtle population differentiation as consequence of post-glacial maximum sea level rise during the Holocene. Main conclusions Our results suggest that anthropogenic activity could have had serious effects on the genetic diversity of heavily exploited littoral species since the end of the Pleistocene, probably accelerating in recent years.