Summary: The influence of massive crude oil contamination on the microbial population of coastal sediments was investigated in the Cíes Islands 18 and 53 months after the tanker Prestige sank off the NW coast of Spain. Communities were studied by means of culturable and non‐culturable methods at three horizons in the sediment (2–5 cm, 12–15 cm and 25–30 cm) in an area heavily affected by the spill. Most probable number of aerobic hydrocarbon degraders was highest in the upper zone and decreased dramatically with depth. Aromatic oxidizing nitrate‐reducing bacteria counts were slightly higher than aerobes in the oxidized layer, and also decreased considerably with depth. Iron‐reducing bacteria were barely detectable. The highest counts were obtained for sulfate‐reducing bacteria, which represented the most relevant fraction of aromatic oxidizers, being maximal at 12–15 cm depth. The community response to high pollution levels was characterized by an increase in culturable populations active towards crude oil components despite the strong decay in the total cell counts. Analysis of whole 16S rRNA gene libraries obtained from the two sampling times and different depths (1460 sequences in all) showed a predominance of Gamma ‐ and Deltaproteobacteria , which was confirmed by fluorescent in situ hybridization. Desulfobacteraceae was the most abundant group among Deltaproteobacteria , followed by sequences affiliated with the order Myxococcales . All retrieved sequences of this order affiliated with a marine myxobacterial clade. Interestingly, sequences affiliated to the order Desulfarculales constituted half of the Deltaproteobacteria sequences retrieved from the heaviest contaminated sample. Principal coordinates analysis of 16S rRNA gene libraries suggested fluctuation in the community distribution with time. Changes in the abundance of certain groups such as Bacteroidetes contributed to these observed differences. Although predominance of certain metabolic types in each horizon could be delimited, a considerable overlap in the use of electron acceptors was observed, confirming that each selected zone could be influenced by more than one respiratory metabolism. Altogether, our results evidence the presence in these sediments of a microbial community with potential to respond against hydrocarbon contamination, consistent with the long pollution history of the site.

Consumption of flavonoids has been associated with protection against cardiovascular and neurodegenerative diseases. Most dietary flavonoids are subjected to bacterial transformations in the gut where they are converted into biologically active metabolites that are more bioavailable and have distinct effects relative to the parent compounds. While some of the pathways involved in the breakdown of flavonoids are emerging, little it is known about the impact of carbon source availability and community dynamics on flavonoid metabolism. This is relevant in the gut where there is a fierce competition for nutrients. In this study, we show that metabolism of one of the most commonly consumed flavonoids, quercetin, by the gut-associated bacterium Eubacterium ramulus is dependent on interspecies cross-feeding interactions when starch is the only energy source available. E. ramulus can degrade quercetin in the presence of glucose but is unable to use starch for growth or quercetin degradation. However, the starch-metabolizing bacterium Bacteroides thetaiotaomicron, which does not metabolize quercetin, stimulates degradation of quercetin and butyrate production by E. ramulus via cross-feeding of glucose and maltose molecules released from starch. These results suggest that dietary substrates and interactions between species modulate the degradation of flavonoids and production of butyrate, thus shaping their bioavailability and bioactivity, and likely impacting their health-promoting effects in humans.

Marine bacteria are considered as promising sources for the discovery of novel biologically active compounds. In this study, samples of sediment, invertebrate and algae were collected from the Providencia and Santa Catalina coral reef (Colombian Caribbean Sea) with the aim of isolating Actinobateria-like strain able to produce antimicrobial and quorum quenching compounds against pathogens. Several approaches were used to select actinobacterial isolates, obtaining 203 strains from all samples. According to their 16S rRNA gene sequencing, a total of 24 strains was classified within Actinobacteria represented by three genera: Streptomyces, Micromonospora, and Gordonia. In order to assess their metabolic profiles, the actinobacterial strains were grown in liquid cultures, and LC-MS-based analyses from ethyl acetate fractions were performed. Based on taxonomical classification, screening information of activity against phytopathogenic strains and quorum quenching activity, as well as metabolic profiling, six out of the 24 isolates were selected for follow-up with chemical isolation and structure identification analyses of putative metabolites involved in antimicrobial activities.