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Oceanography Seminar
Byron Pedler Sherwood
Postdoctoral Scholar
Center for Microbial Oceanography: Research and Education
University of Hawaii at Manoa
"Physiological and ecological constraints on bacterial
turnover of marine dissolved organic matter--insights from a
model system"
The ocean contains one of the largest reservoirs of reduced carbon on Earth in the form of dissolved
organic matter (DOM). The objective of this study was to investigate the physiological and ecological
constraints on microbial mediated DOM turnover by focusing on how a model heterotrophic
bacterial strain makes a living in the sea. It was found that a single strain, Alteromonas sp. AltSIO,
has the capacity to consume an equivalent magnitude of DOC as diverse bacterial communities,
suggesting that bacterial diversity may not be required for the complete removal of labile DOC in the
surface mesotrophic ocean. In long-term microcosms, however, bacterial diversity was required for
continued degradation of semi-labile DOC. To test the generality of this capacity among individual
bacteria, a culture-based study was conducted where >100 phylogenetically diverse bacterial strains
were isolated to screen for growth in unamended ambient DOM. No other bacterial strain tested
exhibited the capacity to consume a measureable quantity of DOC when grown in isolation,
suggesting that this phenomenon may not be common among readily culturable marine bacteria.
Physiological assays and genomic analysis of Alteromonas AltSIO demonstrated a broad capacity for
processing carbohydrates and an apparent preference for disaccharides. DOM characterization by
ultrahigh resolution mass spectrometry revealed that both AltSIO grown in isolation and diverse
seawater communities significantly altered the chemical composition of ambient DOM after 40 days
of incubation. These results will be discussed in the context of an evolving understanding of the
relationship between microbial community composition and the lability of marine DOC.
Thursday
September 4, 2014
3:00 p.m.
MSB 100