• Long-term effects of ocean warming on the prokaryotic community: evidence from the vibrios.

      Vezzulli, Luigi; Brettar, Ingrid; Pezzati, Elisabetta; Reid, Philip C; Colwell, Rita R; Höfle, Manfred G; Pruzzo, Carla; Department for the Study of Territory and its Resources, University of Genoa, Genoa, Italy. luigi.vezzulli@unige.it (2012-01)
      The long-term effects of ocean warming on prokaryotic communities are unknown because of lack of historical data. We overcame this gap by applying a retrospective molecular analysis to the bacterial community on formalin-fixed samples from the historical Continuous Plankton Recorder archive, which is one of the longest and most geographically extensive collections of marine biological samples in the world. We showed that during the last half century, ubiquitous marine bacteria of the Vibrio genus, including Vibrio cholerae, increased in dominance within the plankton-associated bacterial community of the North Sea, where an unprecedented increase in bathing infections related to these bacteria was recently reported. Among environmental variables, increased sea surface temperature explained 45% of the variance in Vibrio data, supporting the view that ocean warming is favouring the spread of vibrios and may be the cause of the globally increasing trend in their associated diseases.
    • Quantitative reverse transcription polymerase chain reaction analysis of Vibrio cholerae cells entering the viable but non-culturable state and starvation in response to cold shock.

      González-Escalona, Narjol; Fey, Axel; Höfle, Manfred G; Espejo, Romilio T; A Guzmán, Carlos; Vaccine Research Group, Division of Microbiology, GBF-German Research Centre for Biotechnology, Braunschweig, Germany. (2006-04)
      We performed a comparative analysis of the Vibrio cholerae strain El Tor 3083 entering the viable but non-culturable (VBNC) state and starvation after incubation in artificial seawater (ASW) at 4 and 15 degrees C respectively. To this end, we determined bacterial culturability and membrane integrity, as well as the cellular levels of 16S rRNA and mRNA for the tuf, rpoS and relA genes, which were assessed by real-time quantitative reverse transcription polymerase chain reaction (Q-RT-PCR). Bacterial cells entering the VBNC state showed a 154, 5.1 x 10(3), 24- and 23-fold reduction in the number of copies of 16S rRNA and mRNA for tuf, rpoS and relA, in comparison to exponentially growing cells. The differences were less striking between cells in the VBNC and starvation states. The mRNA for relA was selectively increased in VBNC cells (3.2-folds), whereas a 3.9-fold reduction was observed for 16S rRNA. The obtained results confirmed that key activities of the cellular metabolism (i.e. tuf representing protein synthesis, and relA or rpoS stress response) were still detected in bacteria entering the VBNC state and starvation. These data suggest that the new Q-RT-PCR methodology, based on the selected RNA targets, could be successfully exploited for the identification (rRNA) of V. cholerae and assessment of its metabolic activity (tuf, rpoS, relA mRNA) in environmental samples.