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Predation on marine pelagic bacteria: On the in situ rates, regulation and dynamics of bacterivory studied with a molecular genetic technique
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). (Johan Wikner)
1989 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Umeå: Umeå universitet , 1989. , 58 p.
Keyword [en]
Marine, grazing, minicells, molecular genetics, method, predation rate, dynamics, bacterivore, predator-prey
National Category
Microbiology
Research subject
Microbiology
Identifiers
URN: urn:nbn:se:umu:diva-52569ISBN: 91-7174-418-5 (print)OAI: oai:DiVA.org:umu-52569DiVA: diva2:506327
Public defence
1989-05-26, Institutionen för Mikrobiologi, Föreläsningssalen, Umeå Universitet 901 87, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2012-03-05 Created: 2012-02-24 Last updated: 2012-03-05Bibliographically approved
List of papers
1. Use of genetically marked minicells as a probe in measurement of predation on bacteria in aquatic environments
Open this publication in new window or tab >>Use of genetically marked minicells as a probe in measurement of predation on bacteria in aquatic environments
1986 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 52, no 1, 4-8 p.Article in journal (Refereed) Published
Abstract [en]

Minicells produced by Escherichia coli M2141 were used as probes to measure predation on pelagic bacteria in situ. The minicells, labeled with [35S]methionine in one specific protein, were shown to disappear in the presence of a microflagellate (Ochromonas sp.), as seen by a decrease in the amount of labeled marker protein with time. Incubation in filtered (pore size, 0.2 μm) and autoclaved seawater did not affect the amount of labeled marker protein in the minicell. The generation time of flagellates feeding on minicells was determined to be similar to that found for flagellates grown on seawater bacteria or living E. coli NC3. Data indicate that minicells are seen as true food particles by the flagellates. The minicell probe was used in recapture experiments, in which predation in situ on pelagic bacteria was demonstrated. The rate of bacterial production showed a clear covariation with the rate of predation, both in different sea areas and in depth profiles. The obtained results (11 field experiments) showed that the rate of predation, on average, accounts for the consumption of 62% of the bacteria produced.

Place, publisher, year, edition, pages
American Society for Microbiology, 1986
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-52562 (URN)A1986D078300002 ()
Available from: 2012-02-28 Created: 2012-02-24 Last updated: 2017-12-07Bibliographically approved
2. Evidence for a tightly coupled nanoplanktonic predator-prey link regulating the bacterivores in the marine-environment
Open this publication in new window or tab >>Evidence for a tightly coupled nanoplanktonic predator-prey link regulating the bacterivores in the marine-environment
1988 (English)In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 50, no 1-2, 137-145 p.Article in journal (Refereed) Published
Abstract [en]

A coupled predator-prey chain, starting with bactenvores, was invest~gated using the mlnicell recapture technique (MiniCap) Water samples were subjected to slze fract~onation wth decreasing filter pore sue in order to obtain a successive truncation of the microbial food chaln Our results showed that the malor bacterivores were flagellates in the size range of 1 to 3 pm The truncation of the food chain caused increased or decreased predation on the bactena, d e p e n d~n go n whether the bacterivores 'ivere released from or subjected to increased predat~on pressure We present a model describing trophic interactions between organisms less than 12 pm In size This model suggests 4 trophic levels to form a regulatory chain exer t~nga tight control on major bacterivores.

Place, publisher, year, edition, pages
Oldenburg: Inter-Research, 1988
National Category
Microbiology
Research subject
Microbiology
Identifiers
urn:nbn:se:umu:diva-52560 (URN)10.3354/meps050137 (DOI)A1988R488000014 ()
Available from: 2012-02-28 Created: 2012-02-24 Last updated: 2017-10-24Bibliographically approved
3. Periodic bacterivore activity balances bacterial-growth in the marine-environment
Open this publication in new window or tab >>Periodic bacterivore activity balances bacterial-growth in the marine-environment
1990 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 35, no 2, 313-324 p.Article in journal (Refereed) Published
Abstract [en]

The grazing rate of pelagic bacteria was repeatedly determined during 36-h time-course experiments with the minicell recapture technique. Die1 variation in the rate of grazing occurred in all water masses investigated. Maximal rates reached 2 x lo5 cells ml-’ h-r, whereas minimal values were 20 times lower. Highest grazing rates were found during the day in most cases, but grazing could also dominate at night as found in one study. Die1 periodicity was mainly due to variation in the per-cell feeding rate of bacterivorous flagellates. Accumulation of the bacterial biomass into the l-3-pm size fraction was positively correlated with changes in bacterial grazing. The transfer efficiency to organisms z 10 pm was low. On average, the daily grazing rate equaled 60% of the bacterial standing stock, exceeding bacterial growth by a factor of 2.6, as estimated from [3H]thymidine incorporation.

Place, publisher, year, edition, pages
American Society of Limnology and Oceanography, 1990
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-52559 (URN)A1990DR94700006 ()
Available from: 2012-02-28 Created: 2012-02-24 Last updated: 2017-10-24
4. Microbial loop in an oligothropic pelagic marine ecosystem: Possible roles of cyanobacteria and nanoflagellates in the organic fluxes
Open this publication in new window or tab >>Microbial loop in an oligothropic pelagic marine ecosystem: Possible roles of cyanobacteria and nanoflagellates in the organic fluxes
Show others...
1988 (English)In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 49, no 1-2, 171-178 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Oldenburg: Inter-Research, 1988
National Category
Microbiology
Research subject
Microbiology
Identifiers
urn:nbn:se:umu:diva-52561 (URN)10.3354/meps049171 (DOI)A1988Q778700017 ()
Available from: 2012-02-28 Created: 2012-02-24 Last updated: 2017-12-07Bibliographically approved

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