Relationship between the Intracellular Integrity and the Morphology of the Capsular Envelope in Attached and Free-Living Marine Bacteria

Abstract

The integrity of the intracellular structures and the presence and dimension of the capsular envelope were investigated in marine snow-associated and marine free-living bacteria by transmission electron microscopy and special fixation techniques. Three categories depending on the presence of internal structures were differentiated. In marine snow, 51% of the marine snow-associated bacterial community was considered intact, 26% had a partly degraded internal structure, and 23% were empty with only the cell wall remaining. For the free-living bacterial community, 34% were intact cells, 42% exhibited damage, and 24% of the cells were lacking any internal structure. We also investigated the morphology and the extent of the bacterial capsular envelope. More than 95% of all intact marine snow-associated bacteria were surrounded by a capsule while Ϸ55% of empty marine snow-associated bacteria had no capsule. For free-living bacteria, Ϸ65% of the intact cells had a capsule while Ϸ80% of the empty free-living bacteria lacked a capsule. Thus there is a clear trend from intact cells which are commonly surrounded by a capsular envelope to empty bacteria for which only the cell wall is remaining. Since bacterioplankton represent the largest living surface in the ocean, it is concluded that the release of intracellular material from bacteria into the environment as well as the release of extracellular capsular material might fuel the dissolved organic matter pool of the ocean.

Grazing rates of bacterivorous protists inhabiting diverse marine planktonic microenvironments

“…In case that this passive mechanism would result in a strength of attachment weaker than that of living bacteria, an overestimation of grazing rates on attached bacteria should be considered. However, during the process of aggregate formation, natural bacteria produce copious amounts of attachment material, which allows not only the attachment of the producer bacteria but also the embedding of planktonic particles (Heissenberger et al 1996). In this work these particles were material present in the natural seawater, such as bacterioplankton, remains of dead organisms, and the added FLB.…”

Lentisphaera araneosa gen. nov., sp. nov, a transparent exopolymer producing marine bacterium, and the description of a novel bacterial phylum, Lentisphaerae

“…The LNHM media used in this study (no MC to 1¥ MC) contained dissolved organic carbon at concentrations that ranged from in situ levels to slightly higher concentrations, but were two to three orders of magnitude less than in commonly used laboratory media . Most EPS excreted by microorganisms have been known to exist as cell surface-bound capsular EPS rather than freely floating slime EPS (Cowen, 1992;Heissenberger et al, 1996). Although the production of EPS, thought to be the main precursors of TEP formation in aquatic environments, is mainly associated with phytoplankton , capsular EPS of bacterial origin also has been observed by transmission electron microscopy in marine snow and seawater samples (Cowen, 1992;Heissenberger et al, 1996).…”

Responses of Bacterial Assemblages on Standing‐Decaying Blades of Smooth Cordgrass to Additions of Water and Nitrogen

“…Note that MUSCHENHEIM et al (1989) found evidence that bacteria attached to particles from smooth-cordgrass shoots moved to the water column in laboratory incubations. Cells having just left the surface of decomposing leaves, where both leaf lysates and algal exudates (FALLON et al, 1985) could be available, might reasonably be expected to be more productive (thymidine incorporation per cell) than most of those in the bacterioplankton (see, e.g., JEFFREY and PAUL, 1986;TURLEY, 1993;AZAM et af., 1994;HEISSENBERGER et al, 1996;SCHUT et al, 1997). Cell emigration might also be involved in the explanation of changes in bacterial morphotypes during tidal excursions onto the marsh (NEWELL and KRAMBECK, 1995).…”