Alcanivorax dieselolei, an alkane-degrading bacterium associated with the mucus of the zoanthid Palythoa caribaeorum (Cnidaria, Anthozoa)

Zoanthid mucus as new source of useful biologically active proteins

Palythoa caribaeorum is a very common colonial zoanthid in the coastal reefs of Brazil. It is known for its massive production of mucus, which is traditionally used in folk medicine by fishermen in northeastern Brazil. This study identified biologically active compounds in P. caribaerum mucus. Crude mucus was collected during low tides by the manual scraping of colonies; samples were maintained in an ice bath, homogenized, and centrifuged at 16,000 g for 1 h at 4 °C; the supernatant (mucus) was kept at -80 °C until use. The enzymatic (proteolytic and phospholipase A₂), inhibitory (metallo, cysteine and serine proteases), and hemagglutinating (human erythrocyte) activities were determined. The results showed high levels of cysteine and metallo proteases, intermediate levels of phosholipase A₂, low levels of trypsin, and no elastase and chymotrypsin like activities. The mucus showed potent inhibitory activity on snake venom metalloproteases and cysteine proteinase papain. In addition, it showed agglutinating activity towards O⁺, B⁺, and A⁺ erythrocyte types. The hemostatic results showed that the mucus prolongs the aPTT and PT, and strongly inhibited platelet aggregation induced by arachidonic acid, collagen, epinephrine, ADP, and thrombin. The antimicrobial activity was tested on 15 strains of bacteria and fungi through the radial diffusion assay in agar, and no activity was observed. Compounds in P. caribaeorum mucus were analyzed for the first time in this study, and our results show potential pharmacological activities in these compounds, which are relevant for use in physiopathological investigations. However, the demonstration of these activities indicates caution in the use of crude mucus in folk medicine. Furthermore, the present or absent activities identified in this mucus suggest that the studied P. caribaeorum colonies were in thermal stress conditions at the time of sample collection; these conditions may precede the bleaching process in zoanthids. Hence, the use of mucus as an indicator of this process should be evaluated in the future.

Hydrocarbonoclastic Alcanivorax Isolates Exhibit Different Physiological and Expression Responses to n-dodecane

Autochthonous microorganisms inhabiting hydrocarbon polluted marine environments play a fundamental role in natural attenuation and constitute promising resources for bioremediation approaches. Alcanivorax spp. members are ubiquitous in contaminated surface waters and are the first to flourish on a wide range of alkanes after an oil-spill. Following oil contamination, a transient community of different Alcanivorax spp. develop, but whether they use a similar physiological, cellular and transcriptomic response to hydrocarbon substrates is unknown. In order to identify which cellular mechanisms are implicated in alkane degradation, we investigated the response of two isolates belonging to different Alcanivorax species, A. dieselolei KS 293 and A. borkumensis SK2 growing on n-dodecane (C12) or on pyruvate. Both strains were equally able to grow on C12 but they activated different strategies to exploit it as carbon and energy source. The membrane morphology and hydrophobicity of SK2 changed remarkably, from neat and hydrophilic on pyruvate to indented and hydrophobic on C12, while no changes were observed in KS 293. In addition, SK2 accumulated a massive amount of intracellular grains when growing on pyruvate, which might constitute a carbon reservoir. Furthermore, SK2 significantly decreased medium surface tension with respect to KS 293 when growing on C12, as a putative result of higher production of biosurfactants. The transcriptomic responses of the two isolates were also highly different. KS 293 changes were relatively balanced when growing on C12 with respect to pyruvate, giving almost the same amount of upregulated (28%), downregulated (37%) and equally regulated (36%) genes, while SK2 transcription was upregulated for most of the genes (81%) when growing on pyruvate when compared to C12. While both strains, having similar genomic background in genes related to hydrocarbon metabolism, retained the same capability to grow on C12, they nevertheless presented very different physiological, cellular and transcriptomic landscapes.

Microbial Communities in Sediments of Lagos Lagoon, Nigeria: Elucidation of Community Structure and Potential Impacts of Contamination by Municipal and Industrial Wastes

Estuarine sediments are significant repositories of anthropogenic contaminants, and thus knowledge of the impacts of pollution upon microbial communities in these environments is important to understand potential effects on estuaries as a whole. The Lagos lagoon (Nigeria) is one of Africa’s largest estuarine ecosystems, and is impacted by hydrocarbon pollutants and other industrial and municipal wastes. The goal of this study was to elucidate microbial community structure in Lagos lagoon sediments to identify groups that may be adversely affected by pollution, and those that may serve as degraders of environmental contaminants, especially polycyclic aromatic hydrocarbons (PAHs). Sediment samples were collected from sites that ranged in types and levels of anthropogenic impacts. The sediments were characterized for a range of physicochemical properties, and microbial community structure was determined by Illumina sequencing of the 16S rRNA genes. Microbial diversity (species richness and evenness) in the Apapa and Eledu sediments was reduced compared to that of the Ofin site, and communities of both of the former two were dominated by a single operational taxonomic unit (OTU) assigned to the family Helicobacteraceae (Epsilonproteobacteria). In the Ofin community, Epsilonproteobacteria were minor constituents, while the major groups were Cyanobacteria, Bacteroidetes, and Firmicutes, which were all minor in the Apapa and Eledu sediments. Sediment oxygen demand (SOD), a broad indicator of contamination, was identified by multivariate analyses as strongly correlated with variation in alpha diversity. Environmental variables that explained beta diversity patterns included SOD, as well as levels of naphthalene, acenaphthylene, cobalt, cadmium, total organic matter, or nitrate. Of 582 OTU identified, abundance of 167 was significantly correlated (false discovery rate q≤ 0.05) to environmental variables. The largest group of OTU correlated with PAH levels were PAH/hydrocarbon-degrading genera of the Oceanospirillales order (Gammaproteobacteria), which were most abundant in the hydrocarbon-contaminated Apapa sediment. Similar Oceanospirillales taxa are responsive to marine oil spills and thus may present a unifying theme in marine microbiology as bacteria adapted for degradation of high hydrocarbon loads, and may represent a potential means for intrinsic remediation in the case of the Lagos lagoon sediments.