The assimilation of amino-acids by bacteria; the action of tyrocidin and some detergent substances in releasing amino-acids from the internal environment of Streptococcus faecalis

Biopesticide and formulation processes based on starch industrial wastewater fortified with soybean medium

The aim of this study was to produce Bacillus thuringiensis-based biopesticide using starch-producing industry wastewater (SIW) fortified with soybean medium and optimize the formulated product using different adjuvants. This study was necessary as low endotoxin concentration is obtained in formulated biopesticide when SIW alone is used as fermentation medium. The fermentation runs were conducted using SIW alone and SIW fortified with 25% soybean (w/v) medium in 2000 L and 150 L bioreactor, respectively. SIW supplemented with soybean medium showed an increase in cell count (from 1.95 × 108 to 1.65 × 109 CFU mL-1), spore synthesis (from 1.5 × 108 to 1.35 × 109 CFU mL-1) and endotoxin concentration (from 436 to 1170 μg mL-1) when compared to SIW medium alone. The fermented broth was concentrated using continuous centrifugation and adjuvants were added for biopesticide formulation in order to enhance its resistance against UV rays and rainfastness. Entomotoxicity of the formulation produced using fermented broth of SIW fortified with soybean (38,000 IU μL-1) was higher than that obtained by SIW medium alone (21,000 IU μL-1), commercial biopesticide Foray 76B (20,000 IU μL-1) and Btk sander's (12,500 IU μL-1).

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems.

The Influence of the Nature of the Recovery Medium on the Apparent Viability of Phenol-Treated Bacteria

Suspensions of Escherichia coli and Staphylococcus aureus, untreated and treated by exposure to phenol, o-cresol or p-chloro-m-cresol, were counted on various types of media. While the counts from untreated suspensions were not affected by the nature of the medium, those from treated suspensions were influenced markedly. There was no correlation between the nutritional status of a medium and its suitability for the cultivation of the treated organisms. Although both bacterial species gave similar patterns of response and ranked the media in roughly the same order of suitability, E. coli was the more responsive species. Generally, the order of suitability was: meat extracts, yeast extracts, meat extract-peptone broth, peptones (all the single ingredients 1 per cent, pH 7; media solidified with New Zealand agar). Although supplementation of the meat extract-peptone control medium, especially with yeast extracts, led to higher counts from treated suspensions, dilution of the extract broth also gave similar results. Further, a fresh infusion broth was superior both to the extract broth and to a digest medium, for counting treated bacteria. The deficiencies of the extract broth were due partly to the phosphate precipitation procedure used in its preparation. The results indicate that when media suitable for the growth of damaged bacteria are required, they should be selected without recourse to preconceived ideas about composition, concentration or method of preparation.

Release of phosphorus-32-containing compounds from Micrococcus lysodeikticus treated with chlorhexidine

Chlorhexidine has been shown to cause the release of cellular constituents from phosphorus-32 labelled cells of Micrococcus lysodeikticus suspended in distilled water or in phosphate buffer. An initial rapid release is followed by a slower secondary release. This secondary release is inhibited by high concentrations of chlorhexidine. The release depends on the chlorhexidine to cell ratio and not on the absolute bactericide concentration.

Comparative Efficacy of Bactericidal Compounds in Buffer Solutions Part II

A number of phenols, aromatic alcohols, organic mercury compounds andquaternary ammoniumcompounds have beenexamined, by the membrane filter method, to assess their antibacterial action at four different pH values against various Gram-positive and Gram-negative organisms. The killing rate of the compounds tested varied with the pH. The phenols, in the undissociated state, and the aromatic alcohols were most effective against Gram-negative cells at a slightly alkaline pH, and least effective at a pH of 5.5 to 7, whereas against Gram-positive cells, the compounds were least bactericidal at a pH of 7 to 8.5 Upon Gram-positive as well as Gram-negative cells, phenylmercuric borate was more potent in alkaline solution, thiomersal, in acid solution. This difference is connected with the opposite charges of the active ions. A reduction in bactericidal activity was noted in acid solutions of domiphen bromide and cetyl pyridinium chloride although the activity of the latter was less influenced by pH. The importance of the partition ratio between water and a lipid phase for the bactericidal efficacy of phenols and aromatic alcohols is stressed, and a new approach to the testing of these compounds is proposed. 4-Chloro- 8- phenylethyl alcohol yielded promising results as a new bactericidal agent. Pseudomonas pyocyanea was more rapidly killed by the compounds tested than Escherichia coli.

Application of the Ferguson principle to the antimicrobial activity of quaternary ammonium salts

The activity of three quaternary ammonium salts, dodecyltrimethylammonium chloride, dodecyldimethylethylammonium chloride and dodecylpyridinium chloride, against M. aureus, E. coli and C. albicans has been determined and correlated with the surface properties of these compounds. The Ferguson principle has been applied by using surface concentration to estimate thermodynamic activity. Results obtained for the three quaternary ammonium salts and a particular micro-organism species were found to be in good agreement with each other when microbiological and surface studies were conducted under identical conditions.

Dynamics of phenol degradation by Pseudomonas putida

Pure cultures of Pseudomonas putida (ATCC 17484) were grown in continuous culture on phenol at dilution rates of 0.074-0.085 h(-1) and subjected to step increases in phenol feed concentration. Three distinct patterns of dynamic response were obtained depending on the size of the step change used: low level, moderate level, or high level. During low level responses no accumulations of phenol or non-phenol, non-glucose-dissolved organic carbon, DOC(NGP), were observed. Moderate level responses were characterized by the transient accumulation of DOC(NGP) with a significant delay prior to phenol leakage. High level responses demonstrated a rapid onset of phenol leakage and no apparent accumulations of DOC(NGP). The addition of phenol to a continuous culture of the same organism on glucose did not result in transient DOC(NGP) accumulations, although transient phenol levels exceeded 90 mg l(-1). These results were consistent with intermediate metabolite production during phenol step tests coupled with substrate-inhibited phenol uptake and suggested that traditional kinetic models based on the Haldane equation may be inadequate for describing the dynamics of phenol degrading systems.

Membrane damage to bacteria caused by single and combined biocides

AIMS

To examine the effect on the leakage of low molecular weight cytoplasmic constituents from Staphylococcus aureus using phenolics singly and in combination, and to see if the observations could be modelled using a non-linear dose response.

METHODS AND RESULTS

The rate of potassium, phosphate and adenosine triphosphate leakage was examined in the presence of chlorocresol and m-cresol. Individually, leakage was observed only at long contact times or high concentrations. Combined at these ineffective concentrations, the cytoplasmic pool of all constituents studied was released within minutes. Both chlorocresol and m-cresol were shown to have non-linear dose responses. A rate model for the combinations, which takes account of these non-linear responses, accurately predicted the observations.

CONCLUSIONS

Antimicrobials, which when used alone exhibit a non-linear dose response, will also give a non-linear dose response in combination. The simple linear-additive model ignores the concept of the dilution coefficient and will always describe the phenomenon of synergy for combinations where one or more of the components has a dilution coefficient greater than one. This has been borne out by examination of the purported prime lesion of chlorocresol and m-cresol, alone and in combination.

SIGNIFICANCE AND IMPACT OF THE STUDY

Studies aimed at producing synergistic mixtures of antimicrobials, which ignore the non-linear additive effect, may waste valuable research effort looking for a physiological explanation for an apparent synergy, where none, in-fact, exists. Patents granted on the basis of analyses using the linear-additive model for combinations of compounds with non-linear dose responses may no longer be supportable.

Eukaryotic transmembrane solute transport systems

A comprehensive classification system for transmembrane molecular transporters has been proposed. This system is based on (i) mode of transport and energy-coupling mechanism, (ii) protein phylogenetic family, (iii) phylogenetic cluster, and (iv) substrate specificity. The proposed "Transport Commission" (TC) system is superficially similar to that implemented decades ago by the Enzyme Commission for enzymes, but it differs from the latter system in that it uses phylogenetic and functional data for classification purposes. Very few families of transporters include members that do not function exclusively in transport. Analyses reported reveal that channels, primary carriers, secondary carriers (uni-, sym-, and antiporters), and group translocators comprise distinct categories of transporters, and that transport mode and energy coupling are relatively immutable characteristics. By contrast, substrate specificity and polarity of transport are often readily mutable. Thus, with very few exceptions, a unified family of transporters includes members that function by a single transport mode and energy-coupling mechanism although a variety of substrates may be transported with either inwardly or outwardly directed polarity. The TC system allows cross-referencing according to substrates transported and protein sequence database accession numbers. Thus, familial assignments of newly sequenced transport proteins are facilitated. In this article I examine families of transporters that are eukaryotic specific. These families include (i) channel proteins, mostly from animals; (ii) facilitators and secondary active transport carriers; (iii) a few ATP-dependent primary active transporters; and (iv) transporters of unknown mode of action or energy-coupling mechanism. None of the several ATP-independent primary active transport energy-coupling mechanisms found in prokaryotes is represented within the eukaryotic-specific families. The analyses reported provide insight into transporter families that may have arisen in eukaryotes after the separation of eukaryotes from archaea and bacteria. On the basis of the reported analyses, it is suggested that the horizontal transfer of genes encoding transport proteins between eukaryotes and members of the other two domains of life occurred very infrequently during evolutionary history.

A functional-phylogenetic classification system for transmembrane solute transporters

A comprehensive classification system for transmembrane molecular transporters has been developed and recently approved by the transport panel of the nomenclature committee of the International Union of Biochemistry and Molecular Biology. This system is based on (i) transporter class and subclass (mode of transport and energy coupling mechanism), (ii) protein phylogenetic family and subfamily, and (iii) substrate specificity. Almost all of the more than 250 identified families of transporters include members that function exclusively in transport. Channels (115 families), secondary active transporters (uniporters, symporters, and antiporters) (78 families), primary active transporters (23 families), group translocators (6 families), and transport proteins of ill-defined function or of unknown mechanism (51 families) constitute distinct categories. Transport mode and energy coupling prove to be relatively immutable characteristics and therefore provide primary bases for classification. Phylogenetic grouping reflects structure, function, mechanism, and often substrate specificity and therefore provides a reliable secondary basis for classification. Substrate specificity and polarity of transport prove to be more readily altered during evolutionary history and therefore provide a tertiary basis for classification. With very few exceptions, a phylogenetic family of transporters includes members that function by a single transport mode and energy coupling mechanism, although a variety of substrates may be transported, sometimes with either inwardly or outwardly directed polarity. In this review, I provide cross-referencing of well-characterized constituent transporters according to (i) transport mode, (ii) energy coupling mechanism, (iii) phylogenetic grouping, and (iv) substrates transported. The structural features and distribution of recognized family members throughout the living world are also evaluated. The tabulations should facilitate familial and functional assignments of newly sequenced transport proteins that will result from future genome sequencing projects.

INACTIVATION OF A BACTERIOPHAGE BY CHEMICAL ANTIBACTERIAL AGENTS

An extinction method has been used to examine the inactivation of coliphage T6r by a number of chemical antibacterial agents. A marked difference in the effect of concentration on inactivation efficiency has been shown for different agents, chloramine-T and formaldehyde having concentration exponents of approximately 2 and 3 respectively; crystal violet, cetrimide and phenol having concentration exponents of approximately 11, 13 and 15 respectively. It is suggested that a low concentration exponent is associated with inactivation of the phage by an effect on the protein coat of the particle and a high concentration exponent with an effect on its internal structure.

Disinfectant induced changes in the antibiotic sensitivity and phage typing pattern in Staphylococcus aureus

Serial passage through disinfectants at sub-minimal inhibitory concentrations induced antibiotic resistances in 30.5% of the derived phenotypic variants of five strains of Staphylococcus aureus. A proportion of these phenotypic variants showed changes in their phage typing pattern by becoming susceptible to an increased number of phages, and a change from phage non-typable to typable was also observed. A loss of temperate phages was noted in some variants when subjected to reverse phage typing.

Gramicidin, valinomycin, and cation permeability of Streptococcus faecalis

Gramicidin and valinomycin in concentrations of 10(-7) and 10(-6)m, respectively, inhibited the growth of Streptococcus faecalis. Inhibition of growth was associated with loss of Rb(+) and K(+) from the cells, and could be reversed by addition of excess K(+). Cells treated with these antibiotics exhibited greatly increased permeability to certain cations; no effect was observed on the penetration of other small molecules. Unlike normal cells, cells treated with gramicidin rapidly lost internal Rb(+) by passive exchange with external cations, including H(+), all monovalent alkali metals, NH(4) (+), Mg(++), and tris(hydroxymethyl)aminomethane. Exchange was rapid even at 0 C and was independent of energy metabolism. The effect of valinomycin was more selective. Cellular Rb(+) was rapidly displaced by external H(+), K(+), Rb(+), and Cs(+); other cations were less effective. The exchange was independent of metabolism but strongly affected by temperature. Under certain conditions, polyvalent cations inhibited exchange between (86)Rb and Rb(+) induced by valinomycin. The antibiotic apparently neither stimulates nor inhibits the energy-dependent K(+) pump of S. faecalis, but exerts its effect on the passive permeability of the membrane to cations. The increased permeability to specific cations induced by gramicidin and valinomycin is a sufficient explanation for the inhibition of growth, glycolysis, and other processes.

SURFACTANTS AS FUNGICIDES

The cationic (Hyamine 3500, Cyprex, or dodine, and Triton X-400), anionic (Atlox G-3300 and Santomerse), and non-ionic (Tritons X-100, X-114, and B-1956 as well as Tween 81) surfactants were compared as inhibitors of respiration, as agents promoting the passage of amino acids out of spores into the surrounding medium, and as inhibitors of germination of the spores of one or more of the test organisms Monilinia fructicola, Alternaria solani, Puccinia recondita, and Puccinia coronata. The loss of cell constituents by leakage caused by the various surfactants paralleled their efficacy as fungicides against A. solani. Although the surfactants do cause reduction in respiration rates paralleling their fungicidal activity, the effect of the compounds on respiratory or other enzyme systems is considered to be secondary to the irreparable damage caused to the semipermeable outer membrane of the cytoplasm. The cations Ni++ and Cu++ were compared with the surfactants as inhibitors of respiration and as stimulators of cell leakage.

The interaction of phenolic compounds with bacteria. I. Hexylresorcinol and Escherichia coli

Various quantitative aspects of the interaction of hexylresorcinol with E. coli suspensions are described. The amounts of hexylresorcinol bound by the bacteria from solutions of varying concentrations were determined and the speed of this reaction and the influence of temperature on the extent of binding examined. The release of cellular constituents from the bacteria and the changes in the light-scattering properties of E. coli suspensions on addition of hexylresorcinol were also investigated. These results are discussed in relation to the site of antibacterial action of hexylresorcinol.