Journal of Conference Abstracts

Bacteriology of Hydrothermal Plumes from the Mid-Atlantic Ridge

Damien O'Brien Department of Microbiology, University College Galway, Ireland

john.d.obrien@ucg.ie

Donal Eardley Department of Microbiology, University College Galway, Ireland

Michael Carton Department of Microbiology, University College Galway, Ireland

John Patching Microbiology Section, Martin Ryan Marine Science Institute, University College Galway, Ireland

Hydrothermal ecosystems have recently become an exciting source of organisms for the microbiologist. An unexpectedly large number of organisms with unique phenotypes, belonging primarily to the domain Archaea, have been isolated from these environments. As most members of natural microbial communities remain unculturable, an assessment of the true extent of these organisms has been limited by reliance on culture-dependant methods. Recent advances in molecular methods based on 16S ribosomal RNA gene sequence analysis and their application to microbial phylogeny now permit a fuller microbial ecology, avoiding the limitations of culture-dependant methods.

We are using these molecular methods to assess the microbial community structure of hydrothermal plumes from the Mid-Atlantic Ridge. Using the polymerase chain reaction, phylogenetically informative 16S ribosomal RNA genes, from both culturable and non-culturable members of the community, are directly isolated from environmental samples obtained by in situ filtration from both inside and outside plumes. These genes are then cloned and sequenced in order to determine the phylogenetic groupings to which they belong. Knowing genetic sequences then permits the design of specific amplification primers and oligonucleotide probes that can be used to determine the occurrence, abundance and distribution of the corresponding organisms in these hydrothermal ecosystems.

In addition, with samples obtained for study from CTD casts into plumes, we have carried out biomass experiments on the plume microbial populations using epifluorescence microscopy. Activity measurements were also carried out under both surface and in situ pressures (using on deck pressure vessels) to determine the degree of adaptation of populations to the plume environment. We have also used scanning electron microscopy coupled with X-ray microanalysis to examine the composition of particulates recovered from plumes and the nature of bacteria/particle associations within the plumes.