Journal of Environmental Science and Health Part A Environmental Science and Engineering and Toxicology

Voordouw G.

The molecular biology of sulfate-redudng bacteria began in 1983 when the gene encoding [Fe] hydrogenase was cloned and sequenced. Since then, a number of genes have been characterized by nucleic acid sequencing. Expression of these genes in functional form was found to be a problem because the host par excellence, Escherichia coli, often failed to synthesize functional holo-proteins. However, genetic systems for conjugation and transduction of sulfate-reducing bacteria have now been developed (Chapter 4), and this achievement has largely solved these expression problems.

von Eichel-Streiber C.

In the nineteenth century a clinical entity accompanied by hemorrhagic diarrhea, designated pseudomembranous colitis (PMC), was first described in a young woman after abdominal surgery (Finney, 1893). As a result of the widespread therapeutic use of antibiotics, similar clinical cases were subsequently reported with increasing incidence (Bartlett and Gorbach, 1977). Because of its induction by antibiotics the disease in its mild form was designated antibiotic-associated diarrhea (AAD). The fatal form of the disease is still known as PMC, after the first reported case.

Mattick J.S., Hobbs M., Cox P.T., Dalrymple B.P.

Dichelobacter nodosus is a gramnegative anaerobe and the essential causative agent of ovine footrot (Egerton, 1977). Virulent isolates of this organism contain large numbers of fine surface filaments termed fimbriae (or common pili) (Figure 39.1), which have a diameter of about 6 nm and may extend up to several micrometers (µm) in length (Stewart, 1973). In other bacteria such fimbriae have been shown to have adhesive properties (Paranchych and Frost, 1988; Moore and Rutter, 1989; see also following) and to represent a primary mechanism for colonization of animal cell surfaces. Although the exact function of D. nodosus fimbriae has not yet been clearly defined, they appear to play a central role in the invasion by the bacterium of the epidermal matrix of the hoof (see Mattick et al., 1985a).

Palmer J.R., Reeve J.N.

Methanogenic bacteria (methanogens) produce methane (natural gas; sometimes called biogas) as the end product of their energy-generating metabolism. This biochemical process, termed methanogenesis, is the rate-limiting and final step in the anaerobic biodegradation of organic compounds. It occurs naturally in freshwater and marine sediments, marshes, paddy fields, geothermal springs, and in the digestive tracts of invertebrates and vertebrates. Termites and ruminants are major sources of biologically produced methane. Approximately 65% of the methane released to the atmosphere, equal to approximately 1% of the atmospheric carbon cycle, is of biological origin; the remainder is produced geologically from wells, mines, and natural vents (Ehhalt, 1974; Daniels, 1984).

Hansen T.A.

In the nearly 100 years that sulfate-reducing bacteria have been studied in pure, or supposedly pure, cultures, our ideas about their carbon metabolism have gone through periods of sometimes slow but occasionally drastic changes. In the past 20 years it has become clear that (1) far more compounds can be oxidized by sulfate reducers than previously thought; (2) organic compounds can be oxidized completely, beyond the level of acetate, to CO2; and (3) some sulfate-reducing bacteria have the potential for fully autotrophic growth. Furthermore, the awareness has grown that a detailed knowledge of their carbon metabolism is required for a proper understanding of the bioenergetic aspects of sulfate reduction and of their role in nature.

Young M.

The conjugative transfer of plasmids between Clostridium perfringens strains was initially described by Sebald and Bréfort in 1975. This was the first demonstration of gene transfer in Clostridia; it was also one of the earliest reports of conjugative gene transfer between gram-positive bacteria. During the past decade, several conjugative elements, both plasmids and transposons, have been identified in the predominantly pathogenic, amino acid-fermenting Clostridia. As the following discussion demonstrates, these indigenous clostridial conjugative elements remain poorly characterized.

Granum P.E., Stewart G.S.

Clostridium perfringens is a large, gram-positive, spore-forming, anaerobic and nonmotile rod belonging to the family Bacillaceae. It is a common inhabitant of the soil and plays an important part in the putrefication process. C. perfringens is also readily isolated from dust, raw meat, water, and the intestinal tract of man and animals, and is the clostridial species most frequently isolated from clinical specimens. Because this organism produces numerous toxins and enzymes, it can cause a spectrum of different diseases in man and animals (for review, see McDonel, 1986). The species is divided into five types based on the production of four major lethal toxins (Table 16.1).

Melasniemi H.

Starch consists of two high molecular mass fractions, amylose and amylopectin, both composed of anhydro glucose units connected to each other by α-glycosidic linkages. In the straight-chain fraction, amylose, there are only α-1,4 linkages, whereas in the branched-chain fraction, amylopectin, short α-1,4 chains are linked to each other by α-1,6 linkages at the branch points. The relative amount of α-1,6 linkages depends on the source of the starch but is approximately 3%–4% in most common starches (Fogarty and Kelly, 1979). α-Amylases (EC 3.2.1.1) hydrolyze α-1,4 linkages in amylose and amylopectin in an endo fashion, producing dextrins and maltooligosaccharides and causing a rapid decrease in the viscosity and iodine-binding capacity of the starch.

Eklund M.W.

Clostridium botulinum and Clostridium novyi are pathogenic anaerobes that are characterized by their ability to produce powerful toxins lethal to man and animals. The different types of C. botulinum are recognized specifically for their ability to produce neurotoxins that are responsible for wound, toxicoinfectious, and food-borne forms of botulism in man and animals. Members of C. novyi do not produce neurotoxins, but they produce other lethal toxins and biologically active substances active in gas gangrene infections found in humans and animals.

Goldfine H.

Among the Clostridia, the most intensively studied group of organisms with respect to lipid composition and metabolism are the saccharo-lytic, butyric acid-producing species. Because the cellular physiology, molecular biology, and genetics of these organisms are currently of considerable interest, a brief review of the status of knowledge of the polar lipids of these organisms is provided. These compounds are intrinsically significant as structural components of the cell membrane; they are also important in terms of modulating membrane protein function. Recent work has shown that these cells have considerable flexibility in regulating their membrane lipids over a wide range of potential environmental and nutritional conditions.

Thomm M., Hausner W.

The investigation of stable RNA sequences has led to the discovery of the Archaebacteria as a second procaryotic line of descent (Woese and Fox, 1977). Archaebacteria are no more related to typical bacteria than to the eucaryotic cytoplasms. Novel designations have been proposed to express this tripartite division of the living world, thus rejecting the conventional procaryote-eucaryote dichotomy (Woese et al., 1990). According to this proposal, life on earth can be seen as comprising three domains, called the Bacteria (formerly eubacteria), the Archaea (archaebacteria), and the Eucarya (eucaryotes).

Bennett G.N., Petersen D.J.

Clostridium acetobutylicum has been used in various circumstances for the production of acetone and butanol from starches for much of this century (for historical review, see Jones and Woods, 1986). Although the availability of petrochemicals has limited the commercial use of the fermentation in the bulk production of butanol and acetone, interest continues in the process from several perspectives. One is the broad substrate specificity of the organism, which allows growth on a wide variety of feedstocks induding some that would otherwise present disposal problems (e.g., cheese whey, apple pomace, and liquors from the paper inductry). Other economic factors include the concomitant production of CO2 and H2, which can be recovered, and the value of the bacterial biomass as animal feed.

Voordouw G., Wall J.D.

Because this chapter is the only one to consider the sulfate-reducing bacteria, it is appropriate to briefly review the classification, as well as some of the nutritional requirements, of the sulfate reducers before discussing their genetics and molecular biology. These topics are by no means isolated from the core of our review, because classification is now greatly advanced by the determination of 16S rRNA sequences with molecular biological methods; an understanding of nutritional requirements is also vital for rapid and efficient plating of these bacteria, which is a prerequisite for the successful application of bacterial genetics.

Wall J.D.

Genetic studies of sulfate-reducing bacteria have lagged far behind physiological and biochemical investigations. The primary reason for this delay has derived from the strictly anaerobic growth mode of these bacteria and the consequent inability to obtain useful plating efficiencies for quantitation of cell numbers (Postgate et al., 1988). Both the improvement of anaerobic chambers that provide a consistently low O2 atmosphere and the selection of strains less sensitive to O2 inhibition have been instrumental in opening sulfate-reducing bacteria to genetic manipulation. Because of the short history of genetics with these bacteria, this review will discuss very basic procedures no longer mentioned in other better analyzed systems.

Minton N.P., Swinfield T., Brehm J.K., Whelan S.M., Oultram J.D.

In the last two decades, interest in using surplus/waste biomass in biocatalytic processes to produce chemicals and fuels of high added value, as an alternative to chemical synthesis from petroleum feedstocks, has exhibited considerable fluctuation. The underlying argument for such developments seems irrefutable. Fossil fuels are a finite resource. It follows that alternative technologies based on a renewable feedstock must eventually be developed. Impetus for undertaking the necessary research has until relatively recently been ruled by economic factors. Thus, although the world oil crisis of the 1970s saw a surge in the fortunes of potential biological processes, a subsequent reduction in petroleum prices dampened initial enthusiasm. Two factors have now refocused the world’s attention on biocatalytic processes.