Search

Microorganisms' retention in soil contributes to the natural purification of groundwater. Bacteria found in groundwater are generally of various shapes. The aim of this study was to assess the importance of cell shape and flagella in bacterial retention during polluted water percolation through two soil columns CA and CB, in the equatorial region in Central Africa. Percolation tests were carried out using different water loads samples which were contaminated by Escherichia coli (straight rods, peritrichous flagella), Vibrio parahaemolyticus (rods bacteria, polar flagella), and Staphylococcus saprophyticus (spherical, free-flagellum). It has been noted that showed that through soil column CA, the mean values of cells retention ratios (T(R)) varied with bacteria species considered, and from one applied water load sample to another. E. coli T(R) and that of S. saprophyticus were not significantly different (P> 0.05) for the two soil columns. V. parahaemolyticus T(R) significantly differed from that of E. coli and S. saprophyticus through soil column CA (P< 0.01) when the highest water load was applied, and through soil column CB (P< 0.05) for each of water load applied. A relative hierarchical arrangement of retained cells based on the T(R) showed that V. parahaemolyticus was less retained through the 2 soil columns. S. saprophyticus in most cases was more retained than others. The physical properties of the bacterial cell must be taken into consideration when evaluating the transfer of bacteriological pollutants towards groundwater. more...

Fluorescently labeled hemocyanin has been previously proposed as an oxygen sensor. In this study, we explored the efficacy of this biosensor for monitoring the biological oxygen consumption of bacteria and its use in testing bacterial cell growth and viability of Escherichia coli, Pseudomonas aeruginosa, Paracoccus denitrificans, and Staphylococcus simulans. Using a microwell plate, the time courses for the complete deoxygenation of samples with different initial concentrations of cells were obtained and the doubling times were extracted. The applicability of our fluorescence-based cell growth assay as an antibacterial drug screening method was also explored. The results provide a proof-of-principle for a simple, quantitative, and sensitive method for high-throughput monitoring of prokaryotic cell growth and antibiotic susceptibility screening. more...

For free-living single-celled organisms, it can be assumed that it is their success in acquiring resources and converting them into cytoplasm that controls the timing of their cell cycles. Cytoplasm is the sink for the bulk of the environmental resources. It must be the case that this type of control must operate in dilute cultures under adequate nutrition in a constant environment. It follows that there ought to be mechanisms that measure or count the cell's biomass or some component of the cytoplasm to measure their growth success. Besides sensing their biomass, they need to know when a certain value of the cell size has been achieved. When this critical state has been achieved, the cell needs to have an all-or-none trigger that either initiates chromosome replication, the completion of cell replication, cell division, or the process of separating sister cells physiologically or physically. Any of these four different stages, in principle, may be the one triggered in response to cell growth in different species of microorganisms. Alternatively, multiple triggers at different cell sizes may be activated at different cell cycle stages. Although initiation of chromosome replication has been believed to be the event triggered in Escherichia coli, this probably is not generally the case and other control mechanisms may act in other prokaryotes. How the increase in cell biomass is self-assessed and used to carry out critical cell cycle events is not understood in any case. This deficiency in our knowledge of microbial cell physiology is grave. The factor that probably has prevented the elucidation of the mechanisms in any organism is that enzymatic processes deal with concentrations, and a cell cycle trigger must respond to the total amount of material present in a cell. This article discusses the theoretically possible classes of mechanisms for the cell to respond when it has achieved its appropriate critical size. These breakdown into three groups: those mechanisms that assess the total amount of biomass or some special subcellular component, and those that measure the ratio of one component to another component where their two syntheses are differently controlled by cell physiology and morphology, and a third group with some specialized mechanisms. more...

Novel bacterial structures have been demonstrated in lysed blood filtrates placed in special culture media from patients with idiopathic hematuria. These structures converted rapidly to gram-positive coccal (streptococcal and staphylococcal-like) coccobacillary and filamentous, bacterial forms in vitro from 96 per cent of the patients studied. Blood cultured conventionally yielded negative findings. Although structures (dense bodies) were demonstrated in normal control blood specimens (albeit in lesser numbers) few converted to classical bacteria in vitro (7 per cent). Erythromycin therapy appeared to correlate with disappearance of hematuria and inability to revert rapidly the variant froms to classical bacteria in vitro. It is suggested that continual bombardment of the blood by bacteria entering from the mouth or other sites may lead to the development of variant bacterial parasitism. In an effort to survive the deleterious host effects the organisms may convert to persisting osmotically stable variant bacterial forms (dense bodies). Development of a disease state may be conditioned by some existing or developing abnormality in the host (immunologic, physiologic and/or biochemical). Furthermore, changes (genetic?) that might take place in the organisms per se during their transition to variant forms and adaptation to life in vivo may not allow certain host environments to adapt to these new forms, possibly leading to a pathogenetic role in renal diseases whose etiologies have long been enigmas. more...

The nature and extent of the immune dysfunctions in 20 immunodeficient patients, as well as the immunocompetence of 22 control subjects, were verified by cell-mediated responsiveness and immunoglobulin quantitations. Comparisons of the microbial composition of supragingival plaque between the two populations showed that a greater number of immunodeficient than control subjects harbored Candida sp. and Staphylococcus sp. Conversely, a lower number of immunodeficient than control subjects harbored Streptococcus mutans. Also, patients with immune dysfunctions had a lower dental caries experience than their immunocompetent counterparts. more...

The present environment of cost containment frequently forces laboratories to reassess various strategies for the diagnostic work-up of patient specimens. The necessity for the performance of antimicrobial susceptibility testing on all morphologic variants of blood culture isolates was examined in this study. Over a 4-year period, of 143 such organisms that were identified, 56 (39%) exhibited clinically significant differences in antibiogram profiles. Coagulase-negative Staphylococcus represented the largest proportion of isolates (n = 115), 39% of which demonstrated clinically significant differences in antibiograms. The authors conclude that these results justify the current practice in their laboratory of performing separate antimicrobial susceptibility testing on all morphologic variants of isolates. more...

Fluorescein isothiocyanate-labeled beta-glucosidase was used as a simple staining reagent with selected gram-positive and gram-negative organisms. Staining in situ appeared to be dependent on the presence of accessible glycosidic-type linkages in the bacterial cell wall. Extensive wall damage or lysis did not occur when stained cells were suspended in washing and mounting solutions. The apparent specificity of labeled enzyme for wall substance was tested by blocking reactions, staining of isolated cell walls, and failure to stain substances lacking appropriate glycosidic linkages. Severe cell wall lesions were produced after prolonged contact with labeled enzyme, and this phenomenon may also be related to staining specificity. Gram-negative organisms and spores were poorly stained unless protected glycopeptide substrate was previously exposed by treatment of cells with thioglycolic acid or dilute alkaline sodium hypochlorite solution. A potential for staining tissues and cell lines may also exist. Some possible applications of labeled enzymes are briefly discussed. more...

A colorimetric method is described whereby the direct quantitative determination of glucosamine, galactosamine and muramic acid can be achieved without previous treatment of the cell-wall hydrolysate, for example by column chromatography. Molar ratios of hexosamines in cell-wall preparations, from a number of bacterial species, determined by this method were found to be in general agreement with previously published results. more...

The production of L forms from cocci, the conditions necessary for their multiplication, and their morphology have been studied for several years. In each strain studied, only a few organisms produced L forms. Transplants from these grew poorly at first, and growth on agar and in broth became abundant only after long cultivation. Multiplication in the form of small granules was observed only when the organisms were embedded in agar and occasionally in coagulated blood serum. On the surface of hard agar, the organisms increased in size but did not multiply. Abundant growth developed on membrane filters of appropriate size, extending into the filters as branching irregular masses. On gelatin, on most samples of coagulated serum, and on silica gel, the organisms grew to a very large size, and occasionally colonies developed by multiplication of large bodies. This multiplication occurred by irregular enlargement and separation into fragments. Growth in broth and in semisolid agar also occurred by multiplication of large bodies, but, in addition, the development of viable granules was observed inside the large bodies in broth culture. After the L forms began to grow abundantly, their nutritional requirements were simple; they no longer required animal serum. Their ability to multiply and their morphological characteristics depended to a large extent on the physical properties of the environment. more...

The use of a synthetic zeolite (type 4A, Union Carbide Corp., Linde Div., New York, N.Y.) in a procedure for the preparation of pure cell wall fractions proved successful for many gram-positive, gram-negative, and acid-fast bacteria, as well as for some fungi. The technique, however, was found to be limited in effectiveness for Rhodospirillum rubrum, Gaffkya tetragena, and Sarcina lutea, and not applicable to preparations of heat killed microorganisms. The possible mechanisms of zeolite action, together with the effect of the disruptive procedure on the chemical composition of cell wall fragments, were investigated also. more...

The bacteriolytic activities in the culture fluid of Myxococcus xanthus were purified and separated into six active fractions by the use of Bio-Gel CM-2 and Bio-Gel P-60. These fractions were identified as: (i) an amidase, (ii) a glucosaminidase, (iii) a glucosaminidase and an amidase, (iv) a protease with probable amidase activity, (v) another protease with probable amidase activity, and (vi) a peptidase active on both d-alanyl-diaminopimelate and d-alanyl-lysine peptide bonds. On one occasion, another amidase was eluted from Bio-Gel CM. Preliminary studies on some characteristics of the enzymes and their production during growth are reported. more...