Marine Bacteria

Alteromonas macleodii is a common marine heterotrophic gamma-proteobacterium. Isolates from this microbe cluster by molecular analysis into two major genotypic groups or ecotypes, one found in temperate latitudes in the upper water column and another that is for the most part found in the deep water column of the Mediterranean. Here, we describe the genome of one strain of the 'deep ecotype' (AltDE) isolated from 1000 m in the Eastern Mediterranean and compare this genome with that of the type strain ATCC 27126, a representative of the global 'surface' ecotype. The genomes are substantially different with DNA sequence similarity values that are borderline for microbes belonging to the same species, and a large differential gene content, mainly found in islands larger than 20 kbp, that also recruit poorly to the Global Ocean Sampling project (GOS). These genomic differences indicate that AltDE is probably better suited to microaerophilic conditions and for the degradation of recalcitrant compounds such as urea. These, together with other features, and the distribution of this genotypic group, indicate that this microbe colonizes relatively large particles that sink rapidly to meso and bathypelagic depths. The genome of ATCC 27126 on the other hand has more potential for regulation (two component systems) and degrades more sugars and amino acids, which is consistent with a more transient particle attachment, as would be expected for lineages specialized in colonizing smaller particulate organic matter with much slower sinking rates. The genomic data are also consistent with a picture of incipient speciation driven by niche specialization.

During screening for biosurfactant-producing, n-alkane-degrading marine bacteria, six heterotrophic bacterial strains were isolated from enriched mixed cultures, obtained from sea water/sediment samples collected near the isle of Borkum (North Sea), using Mihagol-S (C14,15-n-alkanes) as principal carbon source. These Gram-negative, aerobic, rod-shaped bacteria use a limited number of organic compounds, including aliphatic hydrocarbons, volatile fatty acids, and pyruvate and its methyl ether. During cultivation on n-alkanes as sole source of carbon and energy, all strains produced both extracellular and cell-bound surface-active glucose lipids which reduced the surface tension of water from 72 to 29 mN m-1 (16). This novel class of glycolipids was found to be produced only by these strains. The 16S rRNA gene sequence analysis showed that these strains are all members of the gamma-subclass of the Proteobacteria. Their phospholipids ester-linked fatty acid composition was shown to be s...

Epiphytes and fouling organisms induce problems in aquaculture, reducing yield of open-water and on-shore farms. By weighing down materials, fouling can also cause equipment failure. The presence of Ceramium botryocarpum (Rhodophyta, Ceramiales) in tank cultures (Innovalg, France) significantly limits the establishment of opportunist green algae such as Cladophora, Bryopsis or Ulva usually disturbing the cultures. In order to demonstrate the antifouling activity of substances released by C. botryocarpum, the activities of different extracts have been tested on representative marine species such as marine bacteria, phytoplankton, and spores of macroalgae. The extracts from spring strongly inhibit the development of marine bacteria, phytoplankton and spores of Ulva at concentrations between 25 and 150 μg mL − 1 . These results confirm the presence of active substances in C. botryocarpum. No significative trend on the variation in the antifouling activity from September to July has been highlighted. Compared with toxic biocides commonly used in antifouling paints, natural extracts of Ceramium present no cytotoxicity. Active substances from C. botryocarpum could be used to fight against bacterial and algal fouling problems in aquaculture systems.