The potential for bacteria growth in deep sediment layers of the Japan Sea, Hole 798B-Leg 128

Getliff, J. M., Fry, John Christopher, Cragg, Barry Andrew and Parkes, Ronald John 1992. The potential for bacteria growth in deep sediment layers of the Japan Sea, Hole 798B-Leg 128. Proceedings of the Ocean Drilling Program Scientific Results 127/8 (1) , pp. 755-760. 10.2973/odp.proc.sr.127128-1.183.1992

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Abstract

Sediment whole-round cores from between 0.15 and 425 meters below seafloor (mbsf) were obtained, using special techniques to prevent external contamination and maintain anaerobic conditions, to determine the potential for bacterial growth. Samples were taken from the centers of whole-round cores and handled under strict aseptic conditions to prevent contamination and then incubated anaerobically with 1 g/dm3 yeast extract at 15° C. Bacteria were present in all samples prior to incubation and their numbers decreased logarithmically with depth from 9.3 × 108/gat0.15 mbsf to 1.7 × 107/gat425 mbsf. Direct evidence of in-situ growth, as shown by dividing cells, was found in the upper sediments but not below 10 mbsf. Growth was stimulated in all samples except at 9.75 mbsf. Numbers of bacteria increased with time, showing typical growth curves. The frequency of dividing and divided cells (FDDC) increased, and FDDC values were maximal in the midlogarithmic growth phase, as were bacterial productivity estimates calculated from 3H-thymidine incorporation. The absence of growth at 9.75 mbsf may indicate that these bacteria were changing to dormant forms and were under considerable metabolic stress, resulting in substrate accelerated death when a carbon source was added. Bacteria in deep sediments, below 9.75 mbsf, appeared to be largely dormant but were able to grow quickly (within 12 to 96 hr) when incubated with a growth substrate. Extrapolation of the logarithmic growth phase to zero time gave estimates of bacterial viabilities between 0.02% and 35%. These were probably unrealistically high, and considerably higher than those found by other workers using selective media. There was no evidence for contamination of these deep sediment layers by the more active surface sediments during coring. The bacterial distributions and their subsequent growth were consistent with a more comprehensive study of bacterial populations and activity at the same site by Cragg and others. Together, these data demonstrate that bacterial populations can remain viable for very long periods of time, presumably by slowly metabolizing increasingly recalcitrant organic compounds, but can rapidly grow when a suitable growth substrate is supplied.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences
Subjects:	Q Science > QE Geology Q Science > QR Microbiology
Uncontrolled Keywords:	Deep sediment microbiology, bacterial growth, thymidine
Publisher:	Ocean Drilling Program
ISSN:	1096-7451
Last Modified:	12 Jun 2019 02:19
URI:	https://orca.cardiff.ac.uk/id/eprint/8691

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