Microbial ecology

Defining seasonal marine microbial community dynamics Gilbert, J. A. et al. ISME J. 18 Aug 2011 (doi:10.1038/ismej.2011.107)

The past 5 years have seen an explosion in the amount of data describing the diversity of microbial communities in a range of environments. The factors driving this diversity and how it changes over time are some of the key questions facing microbial ecologists. In a recent ISME Journal paper, Gilbert et al. present the latest analysis of a 6-year time series of marine samples taken in the western English Channel, off the coast of Plymouth, UK. Previous work had shown that there is a distinct seasonal structure to the bacterial communities present. This latest paper looks at the biotic and abiotic factors that could influence this seasonality, including the temperature, primary productivity, abundance of phytoplankton and zooplankton, and nutrient concentrations, and concludes that the observed seasonal patterns are most closely correlated with day length.

Bacterial pathogenicity

Recruitment of the major vault protein by InlK: a Listeria monocytogenes strategy to avoid autophagy Dortet, L. et al. PLoS Pathog. 7, e1002168 (2011)

Vault particles are the largest cytoplasmic ribonucleoprotein complexes present in eukaryotic cells. Although they were first identified 25 years ago and there can be thousands of copies per cell, a definitive function has yet to be assigned to these structures. Now, Dortet et al. report that InlK, a previously uncharacterised Listeria monocytogenes effector, interacts with major vault particle protein (MVP), the main protein constituent of vault particles. InlK was shown to be a sortase-anchored bacterial cell surface protein that is expressed in vivo and is required for L. monocytogenes virulence. The interaction with MVP was initially identified in a yeast two-hybrid screen and subsequently confirmed by bacterial pull-down and co-immunoprecipitation assays. Further investigations revealed that the intracytosolic binding of InlK to MVP prevents the recruitment of autophagic markers. The authors conclude that L. monocytogenes can use InlK in addition to ActA to escape recognition by the host autophagy pathway.

Microbial ecology

Hydrogen is an energy source for hydrothermal vent symbioses Petersen, J. M. et al. Nature 746, 176–180 (2011)

Since the discovery of hydrothermal vents more than 30 years ago, research into these fascinating niches has revealed a multitude of interesting chemosynthetic symbioses between bacteria and marine invertebrates, but the only chemosynthetic energy sources to be identified were reduced sulphur compounds and methane. Petersen, Zielinski and co-workers now show that the sulphur-oxidizing gammaproteobacterial symbiont found in the gills of the mussel Bathymodiolus puteoserpentis can use hydrogen as an energy source. Three bacterial partners have been associated with B. puteoserpentis, which is found in the Logatchev vent field in the Mid-Atlantic Ridge, where hydrogen is abundant. Using metagenomics, single-gene fluorescence in situ hybridization and immunohistochemistry, the authors demonstrated that it is the sulphur-oxidizing symbiont that expresses the hydrogenase gene hupL and is responsible for hydrogen use. The authors suggest that the use of hydrogen as an energy source could be common in niches where hydrogen is readily available.