An overview of the sulfate-reduction process is given in Chapter 24. Most types of dissimilatory sulfate-reducing bacteria that have been isolated from nature and described so far are mesophilic, nonsporeforming anaerobes. They are members of the delta subdivision of the proteobacteria. The earliest known representative of this category is Desulfovibrio (Beijerinck, 1895). Further investigations have revealed a great morphological and nutritional diversity within this group. Various cell types have been described including cocci; oval or long straight rods; more or less curved rods or spirilla; cell packets; cells with gas vesicles; and gliding, multicellular filaments (Figs. 7–9). Electron donors used for sulfate reduction include H2, alcohols, fatty acids, other monocarboxylic acids, dicarboxylic acids, some amino acids, a few sugars, phenyl-substituted acids, and some other aromatic compounds (Table 2). Even long-chain alkanes can be anaerobically oxidized by a particular type of sulfate-reducing bacterium (Aeckersberg et al., 1991). The utilization of polysaccharides or polypeptides, such as has been observed with the extremely thermophilic sulfate-reducing archaebacterium Archaeoglobus (Stetter, 1988; Stetter et al., 1987), has not been reported for mesophilic sulfate reducers.

Gram-Negative Mesophilic Sulfate-Reducing Bacteria

Phospholipid, ester-linked fatty acid profiles showed changes in benthic prokaryotic community structure reflecting culture manipulations that were both quantitative and statistically significant. Fatty acid structures, including the position and cis/ trans geometry of double bonds, were chemically verified by GC/MS after appropriate derivatization. The fatty acid profiles of independent flasks showed reproducible shifts when manipulated identically and significant differences when manipulated with different treatments. The absence of polyunsaturated fatty acids indicated that the consortia were predominantly prokaryotic. The prokaryotic consortia of different treatments could be differentiated by the proportions of cyclopropyl fatty acids and the proportions and geometry of monounsaturated fatty acids.

Phospholipid, ester-linked fatty acid profiles as reproducible assays for changes in prokaryotic community structure of estuarine sediments

Dissimilatory Sulfate- and Sulfur-Reducing Prokaryotes

It is generally accepted that the formation of kerogens is the result of the so-called depolymerization-recondensation pathway (Tissot and Welte, 1984; Durand, 1980), Thus, naturally occurring macromolecular substances such as polysaccharides and proteins are enzymatically depolymerized to oligo- and monomers, which for the most part are mineralized. However, a small part of them are thought to condense with other substances such as low-molecular-weight lipids in a random way (Fig. 1). During diagenesis, the “geopolymers” thus formed continuously undergo chemical transformations by which they become more and more insoluble and resistant. Kerogens are being formed, which—depending on the nature of the original organic matter contributions—can generate various amounts and sorts of oil under thermal stress.

A Review of Macromolecular Organic Compounds That Comprise Living Organisms and Their Role in Kerogen, Coal, and Petroleum Formation

Fatty acids of bacterial origin in contemporary marine sediments

The fatty acids obtained from extractable lipids of the anaerobic sulfate bacterium Desulfovibrio desulfuricans were identified. Saturated and monoenoic iso (C15-C19) and anteiso (C15, C17) fatty acids and saturated normal (C14-C18) and monoenoic normal (C16, C18) fatty acids were shown to be shown to be present by capillary gas chromatography-mass spectrometry. Iso and anteiso beta-hydroxy fatty acids were analyzed as trimethylsilyl ethers in the same way. The position of methyl branches in the monoenoic fatty acids was determined from characteristic fragment ions in the mass spectra of their methyl esters. Disilyloxy methyl esters, prepared by derivatization of the mono unsaturated methyl esters and analyzed by capillary gas chromatography-mass spectrometry, provided the position of double bonds. The monoenoic fatty acids identified in this way were normal (delta7-C16:1, delta9-C16:1, delta9-C18:1, delta11-C18:1), iso (delta7-C15:1, delta9-C16:1, delta9-C17:1, delta11-C18:1, delta11-C19:1), and anteiso (delta7-C15:1, delta9-C17:1). Iso delta9-C17:1 fatty acid is present as the major component. The occurrence of these monoenoic fatty acids in this bacterium is of taxonomical importance.

/pdf/significance-and-taxonomic-value-of-iso-and-anteiso-2z6e3o02fa.pdf

Significance and taxonomic value of iso and anteiso monoenoic fatty acids and branded beta-hydroxy acids in Desulfovibrio desulfuricans.

Analytical pyrolysis of carbohydrates: I. Chemical interpretation of matrix influences on pyrolysis-mass spectra of amylose using pyrolysis-gas chromatography-mass spectrometry

The occurrence in sediments of chlorophyll-derived tetrapyrroles provides evidence for primary photosynthetic communities in palaeo water columns. In ancient sedimentary rocks the components occur mainly as nickel or vanadyl complexes of alkyl porphyrins, and to a lesser extent carboxylic acids. Although extensive loss of functional groups has occurred, the structures of a number of the components reveal that chlorophyll carbon skeletons can survive intact or virtually intact, although in other cases the skeletons have been modified by rearrangement. The structures of a few components indicate an origin from the chlorophylls c , and thus an algal input, whereas an origin from photosynthetic bacterial chlorophylls is apparent from the carbon skeletons of other components. Such studies, taken with other distributional features (e.g. ratio of nickel to vanadyl components, extent of tetrapyrrole preservation) can provide information about the productivity and preservation of organic matter and presence of water column anoxia at the time of deposition. Studies of the tetrapyrrole components in one recent and two highly immature older sediments have provided further evidence for the pathway of defunctionalization, through the identification of the minimum number of components necessary to link a chlorophyll, such as chlorophyll a , to the major alkyl porphyrin in sedimentary organic matter. Additionally, evidence for an early and unexpected transformation pathway comes from the recent identification in sediments of chlorin acids esterified with sterols.

Preservation of chlorophyll-derived pigments in sedimentary organic matter

Methyl sugars may become important markers for groups of bacteria living in deposits. The methyl sugars in the Sabkha sediment are presumably released from the lipopolysaccharides of the bacterial cell wall. A large number of lipids with peculiar structures have been encountered for the first time. It is likely that several of these molecules are useful markers for specific microbial communities.

J.J. Boon

Papers

Significance and taxonomic value of iso and anteiso monoenoic fatty acids and branded beta-hydroxy acids in Desulfovibrio desulfuricans.

Analytical pyrolysis of carbohydrates: I. Chemical interpretation of matrix influences on pyrolysis-mass spectra of amylose using pyrolysis-gas chromatography-mass spectrometry

Preservation of chlorophyll-derived pigments in sedimentary organic matter

Biogeochemistry of Gavish Sabkha Sediments. I. Studies on neutral reducing sugars and lipid moieties by gas chromatography-mass spectrometry

Solvent-free and splitless injection method for open tubular columns