Showing papers on "Bacteria published in 1992"

Gram-Negative Mesophilic Sulfate-Reducing Bacteria

Abstract: 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.

Novel method to extract large amounts of bacteriocins from lactic acid bacteria.

Abstract: Antimicrobial peptides, bacteriocins, produced by lactic acid bacteria were adsorbed on the cells of producing strains and other gram-positive bacteria. pH was a crucial factor in determining the degree of adsorption of these peptides onto cell surfaces. In general, between 93 and 100% of the bacteriocin molecules were adsorbed at pHs near 6.0, and the lowest (< or = 5%) adsorption took place at pH 1.5 to 2.0. On the basis of this property, a novel isolation method was developed for bacteriocins from four genera of lactic acid bacteria. By using this method we made preparations of pediocin AcH, nisin, sakacin A, and leuconocin Lcm1 that were potent and concentrated. This method produced a higher yield than isolation procedures, which rely on precipitation of the bacteriocins from the cell-free culture liquor. It is simple and can be used to produce large quantities of bacteriocins from lactic acid bacteria to be used as food biopreservatives.

Molecular and microscopic identification of sulfate-reducing bacteria in multispecies biofilms.

Abstract: The population architecture of sulfidogenic biofilms established in anaerobic fixed-bed bioreactors was characterized by selective polymerase chain reaction amplification and fluorescence microscopy. A region of the 16S rRNA common to resident sulfate-reducing bacteria was selectively amplified by the polymerase chain reaction. Sequences of amplification products, with reference to a collection of 16S rRNA sequences representing most characterized sulfate-reducing bacteria, were used to design both general and specific hybridization probes. Fluorescent versions of these probes were used in combination with fluorescence microscopy to visualize specific sulfate-reducing bacterial populations within developing and established biofilms.

Life after log.

Abstract: A remarkable feature of bacterial species is their capacity for rapid growth when nutrients are available and conditions are appropriate for growth. Perhaps even more remarkable is their ability to remain viable under conditions not propitious for growth. Many bacteria have evolved highly sophisticated mechanisms that allow them to maintain cell viability during starvation and resume growth rapidly when nutrients again become available. Some species form dormant spores, while others form multicellular aggregates and fruiting bodies in response to starvation conditions (26, 34). But even without the formation of such elaborately differentiated cells, many bacteria, among them Escherichia, Salmonella, and Vibrio spp., enter a starvation-induced program that results in a metabolically less active and more resistant state. Examination of starved cells using light microscopy reveals changes in cell morphology. Escherichia coli cells become much smaller and almost spherical when they enter stationary phase (22, 31). This phenomenon is even more striking for a number of marine bacteria which greatly decrease in size during starvation and form ultramicrocells, as small as 0.03 ,um3 (28). Ultramicrocells result from cells that undergo several cell divisions without an increase in biomass and then a further decrease in their size as a result of endogenous metabolism. One possible selective advantage of the reductive divisions seen in marine bacteria is to improve the survival of the clonal population by increasing the probability that some cells will encounter nutrients (38). In E. coli, these changes in cell size and shape are accompanied by changes in the subcellular compartments; the cytoplasm is condensed and the volume of the periplasm increases (48). The surface properties of starved cells are also different from those of growing cells. The surface of many marine bacteria becomes increasingly hydrophobic and the cells become more adhesive during starvation (28). Changes in the fatty acid composition of the cell membranes have been seen during starvation of several species (28). For example, in E. coli there is a conversion of all unsaturated membrane fatty acids to the cyclopropyl derivatives as cells enter stationary phase (14). Vibrio sp. strain S14 acquires new fimbraelike structures and forms cellular aggregates or clumps after prolonged starvation (1). In E. coli, such starvation-induced aggregates appear to form as the result of a self-generated and secreted attractant that is sensed by the chemotaxis machinery (7). The cell wall synthesized during amino acid starvation has

Crystalline bacterial cell-surface layers.

Abstract: Crystalline arrays of proteinaceous subunits forming surface layers (S-layers) are one of the most commonly observed prokaryotic cell envelope structures. They are ubiquitous amongst Gram-positive and Gram-negative archeaobacteria and eubacteria and, if present, account for the major protein species produced by the cells. S-layers can provide organisms with a selection advantage by providing various functions including protective coats, molecular sieves, ion traps and structures involved in cell surface interactions. S-layers were identified as contributing to virulence when present as a structural component of pathogens. In Gram-negative archaeobacteria they are involved in determining cell shape and cell division. The crystalline arrays reveal a broad-application potential in biotechnology, vaccine development and molecular nanotechnology.

Transferrins and heme-compounds as iron sources for pathogenic bacteria.

Abstract: The low concentration of free iron in body fluids creates bacteriostatic conditions for many microorganisms and is therefore an important defense factor of the body against invading bacteria. Pathogenic bacteria have developed several mechanisms for acquiring iron from the host. Siderophore-mediated iron uptake involves the synthesis of low molecular weight iron chelators called siderophores which compete with the host iron-binding glycoproteins lactoferrin (LF) and transferrin (TF) for iron. Other ways to induce iron uptake, without the mediation of siderophores, are the possession of outer membrane protein receptors that actually recognize the complex of TF or LF with iron, resulting in the internalization of this metal, and the use of heme-compounds released into the circulation after lysis of erythrocytes. In this review, the nonsiderophore-mediated iron-uptake systems used by certain pathogenic bacteria are emphasized. The possible contribution of these iron-uptake systems to the virulence of pathogens is also discussed.

Inhibiting factors produced by lactic acid bacteria. 2. Bacteriocins and other antibacterial substances

Abstract: Summary - Lactic acid bacteria can produce a variety of substances with antibacterial activity which are described in this article. Non-peptide antibacterial substances are distinguished from bacteriocins, which have a proteinaceous active site. Among the former, reuterin produced by Lactobacillus reuteri is a broad spectrum inhibitor active against Gram-positive and Gram-negative bacteria, yeasts, molds and protozoas. It is a glycerol derivative, l3-hydroxypropionaldehyde. Bacteriocins can be produced by most lactic acid bacteria species and their spectrum of activity is generally restricted to organisms taxonomically close to the producer. The biochemical properties of bacteriocins, their structure and nature of their genetic determinants are highly variable. This literature review discusses the similarities and differences existing in this group of substances.

Molecular basis for biosynthesis and accumulation of polyhydroxyalkanoic acids in bacteria

Abstract: The current knowledge on the structure and on the organization of polyhydroxyalkanoic acid (PHA)-biosynthetic genes from a wide range of different bacteria, which rely on different pathways for biosynthesis of this storage polyesters, is provided. Molecular data will be shown for genes of Alcaligenes eutrophus, purple non-sulfur bacteria, such as Rhodospirillum rubrum, purple sulfur bacteria, such as Chromatium vinosum, pseudomonads belonging to rRNA homology group I, such as Pseudomonas aeruginosa, Methylobacterium extorquens, and for the Gram-positive bacterium Rhodococcus ruber. Three different types of PHA synthases can be distinguished with respect to their substrate specificity and structure. Strategies for the cloning of PHA synthase structural genes will be outlined which are based on the knowledge of conserved regions of PHA synthase structural genes and of the PHA-biosynthetic routes in bacteria as well as on the heterologous expression of these genes and on the availability of mutants impaired in the accumulation of PHA. In addition, a terminology for the designation of PHAs and of proteins and genes relevant for the metabolism of PHA is suggested.

Lactic Acid Bacteria in Health and Disease

Abstract: I: Lactic Microflora.- 1 The Lactic Microflora of Fowl.- 2 The Lactic Microflora of Pigs, Mice and Rats.- 3 Lactic Acid Bacteria in the Rumen.- 4 The Human Gastrointestinal Tract.- 5 The Lactic Microflora of the Oral Cavity.- II: Lactic Acid Bacteria and Health.- 6 Probiotics: A General View.- 7 The Effect of Probiotics on the Gut Micro-ecology of Farm Animals.- 8 Lactic Acid Bacteria in the Control of Plant Pathogens.- 9 The Antimicrobial Action of Lactic Acid Bacteria: Natural Food Preservation Systems.- 10 Lactic Acid Bacteria and the Control of Tumours.- 11 Lactic Acid Bacteria in the Support of Immunocompromised Hosts.- 12 Fermented Dairy Products and Health.- III: Agriculture and Ecology.- 13 Spoilage in the Sugar Industry.- 14 Lactic Acid Bacteria in Plant Silage.- 15 Storage of Waste Products for Animal Feed.- 16 Lactic Acid Bacteria in Coffee and Cocoa Fermentation.- 17 Sporolactobacilli.- 18 Critical Factors Governing the Competitive Behaviour of Lactic Acid Bacteria in Mixed Cultures.

Human bactericidal/permeability-increasing protein and a recombinant NH2-terminal fragment cause killing of serum-resistant gram-negative bacteria in whole blood and inhibit tumor necrosis factor release induced by the bacteria.

Abstract: The bactericidal/permeability-increasing protein (BPI) of neutrophils and BPI fragments neutralize the effects of isolated Gram-negative bacterial lipopolysaccharides both in vitro and in vivo. Since endotoxin most commonly enters the host as constituents of invading Gram-negative bacteria, we raised the question: Can BPI and its bioactive fragments also protect against whole bacteria? To determine whether the bactericidal and endotoxin-neutralizing activities of BPI/fragments are expressed when Gram-negative bacteria are introduced to the complex environment of whole blood we examined the effects of added BPI and proteolytically prepared and recombinant NH2-terminal fragments on: (a) the fate of serum-resistant encapsulated Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa that survive the antibacterial actions of whole blood and (b) the ability of these bacteria to trigger cytokine release. Added BPI in nanomolar concentrations killed each of three encapsulated strains of E. coli and in closely parallel fashion inhibited tumor necrosis factor (TNF) release. Holo-BPI and its NH2-terminal fragment were equipotent toward a rough LPS chemotype K1-encapsulated strain, but the fragment was substantially more potent than holo-BPI toward two encapsulated smooth LPS chemotype strains. TNF release induced by K. pneumoniae and P. aeruginosa was also inhibited by both holo-BPI and fragment but, at the protein concentrations tested, P. aeruginosa was killed only by the fragment and K. pneumoniae was not killed by either protein. The bactericidal action of BPI/fragment toward E. coli is inhibited by C7-depleted serum, but accelerated by normal serum, indicating that BPI, acting in synergy with late complement components, enhances extracellular killing of serum-resistant bacteria. Thus, BPI and an even more potent NH2-terminal fragment may protect against Gram-negative bacteria in the host by blocking bacterial proliferation as well as endotoxin-mediated effects, not only as components of the intracellular antibacterial arsenal of the neutrophil, but also as potentially therapeutic extracellular agents.

The Human Gastrointestinal Tract

Abstract: The concept of the group name ‘lactic acid bacteria’ was created for bacteria causing fermentation and coagulation in milk, and defined as those which produce lactic acid from lactose. The family name Lactobacteriaceae was applied by Orla-Jensen (1919) to a physiological group of Gram-positive rods and cocci that ferment carbohydrates either to lactic acid alone or to lactic and acetic acids, alcohol and carbon dioxide. Today, lactic acid bacteria are regarded as synonymous by and large with the family Lactobacillaceae (Breed et al.,1957), which is now recognised as consisting of Gram-positive, non-sporing, carbohydrate-fermenting lactic acid producers, acid tolerant, of non-aerobic habit and catalase negative; typically they are non-motile and do not reduce nitrate. They are sub-divided into four genera Streptococcus, Leuconostoc, Pediococcus, and Lactobacillus.

A quantitative model of intracellular growth of Legionella pneumophila in Acanthamoeba castellanii.

Abstract: A model of intracellular growth for Legionella pneumophila in Acanthamoeba castellanii has been developed and provides a quantitative measure of survival and replication after entry. In this model, Acanthamoeba monolayers were incubated with bacteria in tissue culture plates under nutrient-limiting conditions. Gentamicin was used to kill extracellular bacteria following the period of incubation, and the number of intracellular bacteria was determined following lysis of amebae. Intracellular growth of virulent L. pneumophila and other wild-type Legionella species was observed when the assay was performed at 37 degrees C. At room temperature, none of the Legionella strains tested grew intracellularly, while an avirulent L. pneumophila strain was unable to replicate in this assay at either temperature. The effect of nutrient limitation on A. castellanii during the assay prevented multiplication of the amebae and increased the level of infection by Legionella spp. The level of infection of the amebae was directly proportional to the multiplicity of infection with bacteria; at an inoculum of 1.03 x 10(7) bacteria added to wells containing 1.10 x 10(5) amebae (multiplicity of infection of 100), approximately 4.4% of A. castellanii cells became infected. Cytochalasin D reduced the uptake of bacteria by the amebae primarily by causing amebae to lift off the culture dish, reducing the number of target hosts; methylamine also reduced the level of initial infection, yet neither inhibitor was able to prevent intracellular replication of Legionella spp. Consequently, once the bacteria entered the cell, only lowered temperature could restrict replication. This model of intracellular growth provides a one-step growth curve and should be useful to study the molecular basis of the host-parasite interaction.

Extracellular enzymatic activity and secondary production in free-living and marine-snow-associated bacteria

Abstract: Abundance, production (measured as thymidine incorporation) and extracellular enzymatic activity in free-living and marine-snow-associated bacteria were measured in the northern Adriatic Sea. Although bacterial density and production were similar in both free-living and marine-snow-associated bacteria, hydrolytic activity (α- and β-glucosidase and l-aminopeptidase) was significantly higher in marine-snow-associated bacteria, in terms of both absolute and per-cell rates. As concentrations of dissolved total and monomeric carbohydrates and free amino acids in marine snow were very close to those in the ambient water, we suggest that the observed differences between free-living and marine-snow-associated baycteria do not simply reflect catabolic repression of enzyme expression in one of the bacterial components. Whether substrate induction is responsible for the observed higher hydrolase activity in marine-snow bacteria and/or whether there are distinct bacterial species obligatorily associated with marine snow remains unknown.

Metabolism and biochemical characteristics of yogurt bacteria. A review

Abstract: to yogurt manufacture. The taxonomy of these bacteria is presented. Different proposed pathways for carbohydrate metabolism are then discussed, as weil as recent molecular and genetic studies of the enzymes involved. Acetaldehyde is the major aromatic compound in yogurt, and so the different pathways of its formation are briefly described. Recent studies have concerned threonine aldolase which catalyzes acetaldehyde synthesis by yogurt bacteria. Exocellular polysaccharides produced by lactic acid bacteria improve the texture of stirred and liquid yogurts. Some of the polysaccharides of yogurt bacteria are currently known and particular aspects of their production are discussed. Some other properties, le proteolysis, Iipolysis, urease, oxygen metabolism, are also briefly presented. Interactions between streptococci and lactobacilli are weil established, but more data are required for the complete characterization and control of mixed populations. In particular, Iittle is known about antimicrobial compounds produced by these microorganisms. Bacteriophages of yogurt bacteria are now weIl characterized, but liltle is known about Iysogeny in thermophilic streptococci. Finally, progress in genetics (on both plasmid and chromosomal DNA) is briefly discussed.

Sublethal injury makes Gram‐negative and resistant Gram‐positive bacteria sensitive to the bacteriocins, pediocin AcH and nisin

Abstract: Gram-negative and some Gram-positive bacteria that are resistant to bacteriocins of lactic acid bacteria (LAB) were subjected to sublethal stresses and treated with nisin and pediocin AcH. Both bacteriocins reduced the viability of cells surviving sublethal stresses. The results explain the possible mechanisms by which bacteriocins of LAB enter through the walls (or outer membranes) to destabilize the cytoplasmic (or inner) membranes and kill cells of sensitive Gram-positive and resistant, but injured, Gram-negative and Gram-positive bacteria.

Role of human microflora in health and disease.

Abstract: The human host and its microbial flora constitute a complex ecosystem whose equilibrium serves as a remarkable example of reciprocal adaptation. Intestinal bacteria play an important role in the development of the immune system. The normal intestinal flora is responsible for resistance to colonization by exogenous pathogenic microorganisms. Nevertheless, it also constitutes a reservoir of potentially pathogenic bacteria in close contact with the host. These bacteria are responsible for opportunistic infections in immunocompromised hosts. The equilibrium of the flora can be upset by antibiotics, leading to infections as a result of proliferation of antibiotic-resistant pathogenic bacteria.

Two new nitrogen-fixing bacteria from the rhizosphere of mangrove trees: Their isolation, identification and in vitro interaction with rhizosphere Staphylococcus sp.

Abstract: Two new diazotrophic bacteria, Listonella anguillarum and Vibrio campbellii , and one non-nitrogen-fixing bacterium, Staphylococcus sp., were isolated from the rhizosphere of mangrove trees. Strains of these newly-defined diazotrophs are known as pathogenic bacteria in fish and shellfish. During the purification of diazotrophic species from the entire rhizosphere population, N 2 -fixation of the bacterial mixtures decreased. When grown in vitro in mixed cultures, the non-fixing bacterium Staphylococcus sp. increased the nitrogen-fixing capacity of L. anguillarum by 17% over the pure culture; the nitrogen-fixing capacity per bacterial cell increased 22%. This interaction was not due to a change in O 2 concentration. Staphylococcus sp. decreased the nitrogen-fixing capacity of V. campbellii by 15%. These findings indicate that (i) other species of rhizosphere bacteria, apart from the common diazotrophic species, should be evaluated for their contribution to the nitrogen-fixation process in mangrove communities; and (ii) the nitrogen-fixing activity detected in the rhizosphere of mangrove plants is probably not the result of individual nitrogen-fixing strains, but the sum of interactions between members of the rhizosphere community.

Molecular mechanisms of attachment of Rhizobium bacteria to plant roots.

Abstract: Attachment of bacteria to plant cells is one of the earliest steps in many plant-bacterium interactions. This review covers the current knowledge on one of the best-studied examples of bacterium-plant attachment, namely the molecular mechanism by which Rhizobium bacteria adhere to plant roots. Despite differences in several studies with regard to growth conditions of bacteria and plants and to methods used for measuring attachment, an overall consensus can be drawn from the available data. Rhizobial attachment to plant root hairs appears to be a two-step process. A bacterial Ca(2+)-binding protein, designated as rhicadhesin, is involved in direct attachment of bacteria to the surface of the root hair cell. Besides this step, there is another step which results mainly in accumulation and anchoring of the bacteria to the surface of the root hair. This leads to so-called firm attachment. Depending on the growth conditions of the bacteria, the latter step is mediated by plant lectins and/or by bacterial appendages such as cellulose fibrils and fimbriae. The possible role of these adhesions in root nodule formation is discussed.

hrp genes of Pseudomonas solanacearum are homologous to pathogenicity determinants of animal pathogenic bacteria and are conserved among plant pathogenic bacteria.

Abstract: The majority of bacterial plant diseases are caused by members of three bacterial genera, Pseudomonas, Xanthomonas, and Erwinia. The identification and characterization of mutants that have lost the abilities to provoke disease symptoms on a compatible host and to induce a defensive hypersensitive reaction (HR) on an incompatible host have led to the discovery of clusters of hrp genes (hypersensitive reaction and pathogenicity) in phytopathogenic bacteria from each of these genera. Here, we report that predicted protein sequences of three hrp genes from Pseudomonas solanacearum show remarkable sequence similarity to key virulence determinants of animal pathogenic bacteria of the genus Yersinia. We also demonstrate DNA homologies between P. solanacearum hrp genes and hrp gene clusters of P. syringae pv. phaseolicola, Xanthomonas campestris pv. campestris, and Erwinia amylovora. By comparing the role of the Yersinia determinants in the control of the extracellular production of proteins required for pathogenicity, we propose that hrp genes code for an export system that might be conserved among many diverse bacterial pathogens of plants and animals but that is distinct from the general export pathway.

Attachment of plant pathogenic bacteria to plant surfaces.

Abstract: Once a suitable location is reached by a bacterium, the ability to resist removal becomes a selective advantage. Motile bacteria move towards favor­ able locations by chemotactic motility, whereas nonmotile bacteria arrive there more or less randomly. In different kinds of natural environments both motile and nonmotile bacteria tend to stick to surfaces in order to remain at favorable locations. This generalization holds true for animal pathogens (40), aquatic bacteria (24), as well as bacteria in most environments where nutrition is limited or where there is a risk of the cells being dislodged. Characteristics that influence the infective potential of an epiphytically growing bacterium include the ability to withstand drought, UV-radiation, and physical removal from the plant surface through the action of rain and wind. Attachment of bacterial cells to foliage and to the root surface is an early and possibly significant step in certain plant diseases and may represent an important factor in epiphytic colonization, which probably increases the capacity of pathogenic strains to cause plant disease. Bacterial and plant genes and gene products that influence the outcome of plant infections have recently been reviewed (3, 14, 18, 42, 74). The role of attachment for plant-specific bacteria has mostly been studied in relation to virulence of plant pathogens. For some bacteria attachment to a

Gram-positive bacteria with a high DNA G+C content are characterized by a common insertion within their 23S rRNA genes

Abstract: An insertion of about 100 bases within the central part of the 23S rRNA genes was found to be a phylogenetic marker for the bacterial line of descent of Gram-positive bacteria with a high DNA G+C content. The insertion was present in 23S rRNA genes of 64 strains representing the major phylogenetic groups of Gram-positive bacteria with a high DNA G+C content, whereas it was not found in 23S rRNA genes of 55 (eu)bacteria representing Gram-positive bacteria with a low DNA G+C content and all other known (eu)bacterial phyla. The presence of the insertion could be easily demonstrated by comparative gel electrophoretic analysis of in vitro-amplified 23S rDNA fragments, which contained the insertion. The nucleotide sequences of the amplified fragments were determined and sequence similarities of at least 44% were found. The overall similarity values are lower than those of 16S and 23S rRNA sequences of the particular organism. Northern hybridization experiments indicated the presence of the insertion within the mature 23S rRNA of Corynebacterium glutamicum.

Microbial growth on carbon monoxide

Abstract: The utilization of carbon monoxide as energy and/or carbon source by different physiological groups of bacteria is described and compared. Utilitarian CO oxidation which is coupled to the generation of energy for growth is achieved by aerobic and anaerobic eu- and archaebacteria. They belong to the physiological groups of aerobic carboxidotrophic, facultatively anaerobic phototrophic, and anaerobic acetogenic, methanogenic or sulfate-reducing bacteria. The key enzyme in CO oxidation is CO dehydrogenase which is a molybdo iron-sulfur flavoprotein in aerobic CO-oxidizing bacteria and a nickel-containing iron-sulfur protein in anaerobic ones. In carboxidotrophic and phototrophic bacteria, the CO-born CO2 is fixed by ribulose bisphosphate carboxylase in the reductive pentose phosphate cycle. In acetogenic, methanogenic, and probably in sulfate-reducing bacteria, CODH/acetyl-CoA synthase directly incorporates CO into acetyl-CoA.

Identification of distinct communities of sulfate-reducing bacteria in oil fields by reverse sample genome probing.

Abstract: Thirty-five different standards of sulfate-reducing bacteria, identified by reverse sample genome probing and defined as bacteria with genomes showing little or no cross-hybridization, were in part characterized by Southern blotting, using 16S rRNA and hydrogenase gene probes. Samples from 56 sites in seven different western Canadian oil field locations were collected and enriched for sulfate-reducing bacteria by using different liquid media containing one of the following carbon sources: lactate, ethanol, benzoate, decanoate, propionate, or acetate. DNA was isolated from the enrichments and probed by reverse sample genome probing using master filters containing denatured chromosomal DNAs from the 35 sulfate-reducing bacterial standards. Statistical analysis of the microbial compositions at 44 of the 56 sites indicated the presence of two distinct communities of sulfate-reducing bacteria. The discriminating factor between the two communities was the salt concentration of the production waters, which were either fresh water or saline. Of 34 standards detected, 10 were unique to the fresh water and 18 were unique to the saline oil field environment, while only 6 organisms were cultured from both communities.

Comparative acid tolerances and inhibitor sensitivities of isolated F-ATPases of oral lactic acid bacteria.

Abstract: pH activity profiles and inhibitor sensitivities were compared for membrane ATPases isolated from three oral lactic acid bacteria, Lactobacillus casei ATCC 4646, Streptococcus mutans GS-5, and Streptococcus sanguis NCTC 10904, with, respectively, high, moderate, and low levels of acid tolerance. Membranes containing F1F0 ATPases were isolated by means of salt lysis of cells treated with muralytic enzymes. Membrane-free F1F0 complexes were then isolated from membranes by detergent extraction with Triton X-100 or octylglucoside. Finally, F1 complexes free of the proton-conducting F0 sector were obtained by washing membranes with buffers of low ionic strength. The pH activity profiles of the membrane-associated enzymes reflected the general acid tolerances of the organisms from which they were isolated; for example, pH optima were approximately 5.5, 6.0, and 7.0, respectively, for enzymes from L. casei, S. mutans, and S. sanguis. Roughly similar profiles were found for membrane-free F1F0 complexes, which were stabilized by phospholipids against loss of activity during storage. However, profiles for F1 enzymes were distinctly narrower, indicating that association with F0 and possibly other membrane components enhanced tolerance to both acid and alkaline media. All of the enzymes were found to have similar sensitivities to Al-F complexes, but only F1F0 enzymes were highly sensitive to dicyclohexylcarbodiimide. The procedures described for isolation of membrane-free F1F0 forms of the enzymes from oral lactic acid bacteria will be of use in future studies of the characteristics of the enzymes, especially in studies with liposomes.