SEARCH · PubMed Health

Results for “Bacteria”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2024

Filamentous bacteria-induced sludge bulking can alter antibiotic resistance gene profiles and increase potential risks in wastewater treatment systems.

Sludge bulking caused by filamentous bacteria is a prevalent issue in wastewater treatment systems. While previous studies have primarily concentrated on controlling sludge bulking, the biological risks associated with it have been overlooked. This study demonstrates that excessive growth of filamentous bacteria during sludge bulking can significantly increase the abundance of antibiotic resistance genes (ARGs) in activated sludge. Through metagenomic analysis, we identified specific ARGs carried by filamentous bacteria, such as Sphaerotilus and Thiothrix, which are responsible for bulking. Additionally, by examining over 1,000 filamentous bacterial genomes, we discovered a diverse array of ARGs across different filamentous bacteria derived from wastewater treatment systems. Our findings indicate that 74.84% of the filamentous bacteria harbor at least one ARG, with the occurrence frequency of ARGs in these bacteria being approximately 1.5 times higher than that in the overall bacterial population in activated sludge. Furthermore, genomic and metagenomic analyses have shown that the ARGs in filamentous bacteria are closely linked to mobile genetic elements and are frequently found in potentially pathogenic bacteria, highlighting potential risks posed by these filamentous bacteria. These insights enhance our understanding of ARGs in activated sludge and underscore the importance of risk management in wastewater treatment systems.

Sewage↗

PubMed1976

Degradation of blood group antigens in human colon ecosystems. II. A gene interaction in man that affects the fecal population density of certain enteric bacteria.

The autosomal dominant ABH secretor gene together with the ABO blood type gene control the presence and specificity of A, B, and H blood group antigens in human gut mucin glycoproteins. Certain obligate anaerobes in feces produce extracellular antigen-specific glycoside structures. We estimated the populations of these bacteria in feces of 22 healthy subjects by determining the greatest dilution of feces that yielded A, B, or H blood group-degrading enzyme activity after 24 h incubation in anaerobic cultures. Comparatively small populations of fecal bacteria produce blood group-degrading enzymes; their estimated populations were 10(8) per g or less in 21 subjects. Fecal populations of B-degrading bacteria were stable over time, and their population density averaged 50,000-fold greater in blood group B secretros than in other subjects. We present evidence that the greater fecal populations of B-degrading bacteria in B secretors is due in part to a competitive nutritional advantage gained by their ability to enzymatically cleave the B antigenic determinant alpha-D-galactose from gut mucins of B secretors. Fecal populations of bacteria producing A and H antigen-degrading enzyme activities were comparable in all subjects to the fecal population of B-degrading bacteria in B secretors. The large populations of fecal anaerobes may be an additional source of A antigen substrate for A-degrading bacteria; thus, antigens cross-reacting with A antigen were detected on cell walls of anaerobic bacteria from 3 of 10 cultures inoculated with 10(-10) g feces. Bacteria producing B-degrading activity likely represent a separate population from those producing A- or H-degrading activity since their fecal populations differed numerically in 14 subjects. These findings suggest that adaptation of blood group-degrading enzymes to mucin structures in human colon ecosystems is chiefly by mutation-selection of comparatively small populations of constitutive enzyme-producing strains rather than by substrate induced enzyme synthesis in many strains.

ABO Blood-Group System↗

PubMed1978

Effect of ionizing radiation of the antigenic composition of typhoid bacteria.

Changes in the antigenic composition of typhoid bacteria occurring during the exposure of microbial suspension to different doses of gamma irradiation [Co60] ranging between 0.5 and 3.0 Mrad were studied. Immunoelectrophoresis in agar was used to determine the antigenic composition of different samples of irradiated bacteria. The antigenic composition of bacteria irradiated with doses up to 2.5 Mrad was found to be similar to that of non-irradiated bacteria. Antigens demonstrated by means of Vi, H and O ontisera are preserved in these bacteria. However, all irradiated bacteria in general slightly differ from non-irradiated bacteria; this is manifest in a different configuration and position of the precipitation lines in the cathodic part of the immunophoreograms. The content of the component migrating rapidly towards the cathode, evidently the O antigen in the R form, in the irradiated bacteria increases with the dose of radiation. No new serologically active substances, non-existent in non-irradiated bacteria, were found to appear in the process of irradiation.

Antigens, Bacterial↗

PubMed1978

Maintenance requirements for bacteria growing on C1-compounds.

The maintenance coefficient, ms (mmol substrate/g cell dry wt hr), of two distinct groups of C1-utilizing bacteria has been determined by growing the organisms in an aerobic continuous culture limited by different C1 growth substrates. For growth on methanol, ms = 2.5 +/- 0.3 for Pseudomonas C; 3.9 +/- 0.7 for Ps. methylotropha (these bacteria utilize methanol via the ribulose monophosphate pathway of formaldehyde fixation); 1.5 +/- 0.2 for Pseudomonas 1, and 2.3 +/- 0.4 for Pseudomonas 135 (the latter bacteria utilize C1-compounds via the serine pathway). For growth on formaldehyde, ms = 1.5 +/- 0.3 for Pseudomonas 1 and 2.7 +/- 0.7 for Pseudomonas 135, whereas on formate the values for ms are 1.0 +/- 0.2 and 4.4 +/- 1.3; respectively. Although the maintenance coefficients did not differ systematically between the two groups of bacteria, the maintenance requirements per generation of the serine pathway bacteria were considerably higher (8.7 vs. 3.9) owing to their slower growth rate. The maximum molar yield values, YMmax (g cell dry wt/mol substrate utilized), corrected for the maintenance energy of bacteria which utilize C1-compounds via the ribulose monophosphate pathway averaged 19.1 when grown on methanol, while the values for bacteria which use the serine pathway averaged 13.5. On formaldehyde an average value of 11.5 is obtained and on formate the average value was 7.4 in the serine pathway bacteria.

Adenosine Triphosphate↗

PubMed2024

Contaminant-degrading bacteria are super carriers of antibiotic resistance genes in municipal landfills: A metagenomics-based study.

Municipal landfills are hotspot sources of antimicrobial resistance (AMR) and are also important habitats of contaminant-degrading bacteria. However, high diversity of antibiotic resistance genes (ARGs) in landfills hinders assessing AMR risks in the affected environment. More concerned, whether there is co-selection or enrichment of antibiotic-resistant bacteria and contaminant-degrading bacteria in these extremely polluted environments is far less understood. Here, we collected metagenomic datasets of 32 raw leachate and 45 solid waste samples in 22 municipal landfills of China. The antibiotic resistome, antibiotic-resistant bacteria and contaminant-degrading bacteria were explored, and were then compared with other environmental types. Results showed that the antibiotic resistome in landfills contained 1,403 ARG subtypes, with the total abundance over the levels in natural environments and reaching the levels in human feces and sewage. Therein, 49 subtypes were listed as top priority ARGs for future surveillance based on the criteria of enrichment in landfills, mobilizable and present in pathogens. By comparing to those in less contaminated river environments, we elucidated an enrichment of antibiotic-resistant bacteria with contaminant-degrading potentials in landfills. Bacteria in Pseudomonadaceae, Moraxellaceae, Xanthomonadaceae and Enterobacteriaceae deserved the most concerns since 72.2 % of ARG hosts were classified to them. Klebsiella pneumoniae, Acinetobacter nosocomialis and Escherichia coli were abundant multidrug-resistant pathogenic species in raw leachate (∼10.2 % of total microbiomes), but they rarely carried contaminant-degradation genes. Notably, several bacterial genera belonging to Pseudomonadaceae had the most antibiotic-resistant, pathogenic, and contaminant-degrading potentials than other bacteria. Overall, the findings highlight environmental selection for contaminant-degrading antibiotic-resistant pathogens, and provide significant insights into AMR risks in municipal landfills.

Metagenomics↗

PubMedDate not supplied

From penicillin-binding proteins to the lysis and death of bacteria: a 1979 view.

The mechanism by which interference with the biosynthesis of bacterial cell wall causes death and lysis of bacteria appears more complex than originally thought. In an earlier model of the mode of action of beta-lactams, it was assumed that, in the presence of the antibiotics, bacteria synthesize a mechanically weak (poorly cross-linked) cell wall that ruptured under the osmotic-mechanical pressure of the normally growing cytoplasmic mass. However, recent findings suggest a much more complex picture. Lysis and, in at least some bacteria, loss of viability as well, seem to be catalyzed by autolytic enzymes (murein hydrolases), the destructive activity of which is triggered in the beta-lactam-treated bacterium via a poorly understood mechanism. Furthermore, different species of bacteria respond quite differently to treatment with the same beta-lactam: some bacteria are both killed and lysed, others only lose viability, whereas still other species respond mainly by a reversible inhibition of growth (beta-lactam-tolerant bacteria). In addition, structurally different beta-lactams may cause quite different biochemical, morphological, and antibacterial effects, even within the same bacterial species. It is conceivable, therefore, that there is more than one mechanism for loss of viability and/or lysis. Most of the bacteria examined so far contain a number (four to eight) of different penicillin-binding proteins. Genetic and physiological evidence obtained in E. coli indicate that these proteins play essential roles in a variety of physiological functions, such as maintenance of structural integrity, shape, and cell division. Pneumococci with a suppressed autolytic system are resistant to he lytic (and, partially at least, to the bactericidal) effect of beta-lactams. Interference with cell wall synthesis seems to trigger autolysin activity by upsetting the cellular control of autolytic enzyme. It is suggested that the irreversible antimicrobial effect of beta-lactams may have an indirect mechanism in other bacteria as well.

Animals↗

PubMedDate not supplied

[Species composition of heterotrophic bacteria in the water of the Rybinek reservoir].

Twenty four cultures of heterotrophic bacteria were isolated from the water of the Rybinsk Reservoir on a medium containing organic matter. Bacteria belonging to the families Pseudomonadaceae and Achromobacteriaceae were most widely distributed; bacteria of the Mycobacteriaceae family were encountered less often. Predominating species which belonged to the genera Pseudomonas, Caulobacter, Flavobacterium, Mycobacterium, and Corynebacterium were isolated from the central part of the Reservoir. The special composition depended on the season. Bacteria of the Caulobacter genus were isolated mainly by the end of July and in May. Bacteria of the Corynebacterium genus predominated in March. Microflora belonging to the genera Pseudomonas and Flavobacterium was more constant. Bacteria isolated on media with the minimum content of organic matter (0.5 mg C per litre) belonged mainly to the Pseudomonas genus. Morphological, cultural, and physiological properties of the bacteria were studied. The bacteria grew on media containing carbohydrates and alcohols as a source of carbon though organic acids were assimilated to a less extent. The activity of catalase was found in the cultures, with an exception of the genera Caulobacter and Achromobacter.

Bacteria↗

PubMed1978

[Anaerobic bacteria in digestive surgery. Pathogenic role and prognostic incidence (author's transl)].

The authors isolated in common surgical practice 83 anaerobic bacteria mainly bacteroides and clostridia. They analyse their pathogenic role in relation to the site of sampling. Comparing the bacteriological results with a clinical study of 96 cases of generalised peritonitis, there appeared to be no significant differente between the prognosis in peritonitis and anaerobic bacteria and those without anaerobic bacteria. The mortality was identical in septicemia due to anaerobic and aerobic bacteria; jaundice was just as frequent in both series. However, the prognosis of peritonitis due to anaerobic bacteria seems better when antibiotic treatment is adapted to the bacteria, e.g. lincomycin, metronidazole. With regard to anaerobic bacteria, which represent only part of the fecal flora, it may be dangerous by selection of resistant strains to use prophylactic antibiotics as a routine; local treatment of the septic focus seems the most important. The pathogenic role of anaerobic bacteria in digestive pathology is far from clearly defined; one should not follow the fashion of using even specific antibiotics without justification.

Adolescent↗

PubMed1978

Nitrogen fixation and hydrogen metabolism in photosynthetic bacteria.

The photosynthetic bacteria are found in a wide range of specialized aquatic environments. These bacteria represent important members of the microbial community since they are capable of carrying out two of the most important processes on earth, namely, photosynthesis and nitrogen fixation, at the expense of solar energy. Since the discovery that these bacteria could fix atmospheric nitrogen, there has been an intensification of studies relating to both the biochemistry and physiology of this process. The practical importance of this field is emphasized by a consideration of the tremendous energy input required for the production of artificial nitrogenous fertilizer. The present communication aims to briefly review the current state of knowledge relating to certain aspects of nitrogen fixation by the photosynthetic bacteria. The topics that will be discussed include a general survey of the nitrogenase system in the various photosynthetic bacteria, the regulation of both nitrogenase biosynthesis and activity, recent advances in the genetics of the nitrogen fixing system, and the hydrogen cycle in these bacteria. In addition, a brief discussion of some of some of the possible practical applications provided by the photosynthetic bacteria will be presented.

Bacteria↗

PubMed1977

The metabolism of starch, glucose, amino acids, purines, pyrimidines and bacteria by the rumen ciliate Polyplastron multivesiculatum.

The large rumen ciliate protozoon Polyplastron multivesiculatum grown in vitro engulfed a wide range of bacteria (from a population density of 10(9) bacteria ml(-1)) at a rate of 1500 to 137000 bacteria h(-1) protozoon(-1). No evidence was found for the preferential engulfment of bacteria of rumen origin. Except for Proteus mirabilis none of the bacteria were digested with the liberation of soluble materials into the medium. Glucose and amino acids were taken up rapidly by P. multivesiculatum compared with the rate of uptake by Entodinium caudatam. Glucose was incorporated into protozoal polysaccharide and into bacteria associated with the protozoa and was used for the synthesis of a wide range of amino acids. Evidence showed that bacteria and free amino acids at the concentrations found in the rumen could supply the protein requirements of the protozoa for division at least once each day.

Amino Acids↗

PubMed1977

Isolation of drug-resistant bacteria from newborn infants.

The fetus is known to be bacteria-free and is contaminated with bacteria during birth. We examined drug-resistant bacteria in feces of new-born infants to know the distribution of drug-resistant bacteria in a hospital. Among 76 infants examined, we could isolate drug-resistant strains of bacteria from 65 infants (86%). We collected 110 drug-resistant strains of Escherichia coli, Klebisella pneumoniae, and Pseudomonas aeruginosa, and could isolate 53 strains (48%) carrying R plasmids; they being 33R (TC.CM.SM.SA.APC) and 20R (TC.CM.SM.SA) plasmids. The data indicated that R plasmids with the same resistance patterns were distributed in a hospital, and new-born infants were contaminated with bacteria carrying R plasmids, although the contamination rate of drug-resistant bacteria in the intestinal flora was very low.

Bacteria↗

PubMed1977

Significance of antibody-coated bacteria in urinary sediment in experimental pyelonephritis.

The sequential appearance of antibody-coated bacteria in urinary sediment was followed in experimental pyelonephritis produced with Escherichia coli O6:K13:H1. It was possible to determine against which antigen of the organism this antibody was directed. Antibody-coated bacteria appeared by day 11 of infection, a time which coincided with the synthesis of local (intrarenal) antibody. Bacteria coated with antibody more than three days after serum antibody but four days before urinary antibody appeared. Antibody eluted from coated bacteria was directed against the O-antigen of the infecting organism but not the K-antigen. Newly synthesized intrarenal antibody and urinary antibody were directed only against O-antigen, but not against K-antigen; this finding would explain why the antibody that coated the bacteria was antibody to lipopolysaccharide. Thus, a positive test for antibody-coated bacteria indicates that a local immune response to O-antigen has occurred. It is postulated that this immune response could relate to the clinical symptomatology of acute symptomatic pyelonephritis since most patients presenting with acute pyelonephritis have bacteria coated with antibody.

Animals↗

PubMed1977

Survival of bacteria from human dental plaque under various transport conditions.

The effects of transport media, temperature, and anaerobiosis on the survival of bacteria from human supragingival dental plaque were studied. Individual samples were obtained by passing sterile, unwaxed dental floss through the interproximal spaces. The plaque-bearing portion of floss was immediately placed in vials containing reduced transport fluid, viability-preserving microbistatic medium, or reduced salt solution transport fluid. Plaque samples were dispersed by ultrasonic oscillation, serially diluted, and plated in duplicate on MM10-sucrose-blood agar, mitis salivarius bacitracin agar, and Rogosa tomato juice agar. Initial viable counts (time 0) were compared with viable count determinations after 48- and 72-h storage. Quantitative recovery (>30%) of various groups of oral bacteria was accomplished from both reduced transport fluid and viability-preserving microbistatic medium after 48- and 72-h storage. Storage of dental plaque in reduced salt solution proved unsatisfactory for most bacteria (less than 10% survival). Since growth of some bacteria may occur in viability-preserving microbistatic medium and the charcoal present interferes with colonly enumeration on low-dilution plates, we found reduced transport fluid to be the most suitable medium for transport and recovery of bacteria from supragingival dental plaque. Subzero storage (-196 and -40 degrees C) did not enhance the survival of bacteria from dental plaque; storage at moderate (5 and 20 degrees C) temperatures gave better recovery of viable bacteria. Survival after anaerobic or aerobic storage was comparable for total colony-forming units; however, anaerobic storage enhanced survival of Streptococcus mutans and Lactobacillus. Since these organisms are specifically associated with dental caries, anaerobic techniques are preferred for caries activity testing of plaque.

Aerobiosis↗

PubMed1978

Antibody-coated bacteria in the urinary sediment of rats with experimental pyelonephritis.

The appearance of antibody-coated bacteria in urinary sediment has been evaluated in rats with experimental pyelonephritis. At day 7 after induction of pyelonephritis, 9 out of 11 rats demonstrated antibody-coated bacteria in the urinary sediment. The other 2 rats never had a positive urinary sediment. Following removal of the pyelonephritic kidneys, antibody-coated bacteria disappeared in 7 of 9 previously positive rats. In the 2 rats which continued to show antibody-coated bacteria, the infecting organisms were found in the remaining kidney. The 2 rats which never developed antibody-coated bacteria in urinary sediment had a higher then normal serum antibody titer, and 1 rat with antibody-coated bacteria showed a normal serum antibody titer. It is concluded that although the search for antibody-coated bacteria in urinary sediment is a very useful technique, its negativity does not exclude upper urinary tract involvement; in the case of renal parenchymal infection, immunity is not the same at the systemic and the local site.

Animals↗

PubMed1979

Influence of culture medium of the fatty-acid profile in enteric bacteria.

Enteric bacteria having a high content of cyclopropane fatty acids steeply increase their synthesis when grown on insufficiently propitious culture media (meat-peptone agar or modified Drobot'ko synthetic medium) as compared with bacteria grown under more favourable conditions (meat-peptone broth). Simultaneously, a decrease in monounsaturated fatty acids and increase in palmitic acid are observed. One of the main factors underlying the change in the proportion of fatty acids in bacteria grown on synthetic medium is an increase in medium pH in the process of their growth. Enteric bacteria containing minute amounts/or not containing cyclopropane fatty acids at all (under the experimental conditions used) change their fatty-acid profile little if the culture medium is changed. When grown under insufficiently favourable conditions, these bacteria mainly display an enhanced content of palmitic acid and a lowered content of octadacenoic acid as compared with bacteria grown under more favourable conditions. Of the culture media used, meat-peptone broth, which affords the most favourable conditions for eneteric bacteria growth, is the most suitable medium for obtaining data of taxonomic value.

Culture Media↗

PubMed1979

Attachment of bacteria to soft contact lenses.

A total of 25 soft contact lenses from 17 asymptomatic contact lens wearers and eight patients with contact lens-associated giant papillary conjunctivitis were examined by scanning electron microscopy. Structures that resembled bacteria were present on the anterior surface of seven lenses. All lenses showed a coating of granular mucus-like deposits. Some bacteria were seen scattered randomly over the surface, with no apparent attachment to the lens, whereas others were attached to the coated surface by thin, flagella-like foot processes, the distal ends of which were unattached. These attached bacteria were cylindrical in shape. Several bacteria showed a constriction centrally. Some bacteria were covered by the surface coating, while others, which were round to ovoid in shape, appeared partially embedded in the coating itself. Aggregations of bacteria were seen around clumps of mucus-like debris.

Bacteria↗

PubMed2025

Single-Cell Force Spectroscopy Uncovers Root Zone- and Bacteria-Specific Interactions.

Understanding root-bacteria interactions with plant growth-promoting rhizobacteria (PGPR) is key to developing effective biofertilizers for sustainable agriculture. We performed single-cell force spectroscopy using the atomic force microscope (AFM) to study the primary attachment of two PGPR, Bacillus velezensis and Pseudomonas defensor, to different regions of Arabidopsis thaliana roots. Force measurements with individual cells uncovered distinct attachment strategies by each strain, involving binding via micrometer-long polymers from both bacteria and root surfaces. Flagella differentially affected the binding interactions of each PGPR; their removal altered binding characteristics differently for each strain, highlighting the importance of flagella in early root colonization. Using silica beads to mimic the negatively charged bacteria, we demonstrated the influence of electrostatic forces on root-bacteria interactions. We also examined interactions with abiotic surfaces of varying surface energies, revealing the roles of hydrophilic and hydrophobic forces in initial binding. Our measurements show that differences in the physicochemical properties of bacteria and roots are responsible for variations in primary attachment strategies between PGPR strains and root regions. Parallel fluorescence measurements corroborated our AFM single-cell analysis. Overall, our results provide a nanoscale view of bacterial attachment to roots, offering key insights into how beneficial bacteria colonize roots, crucial for enhancing biofertilizer effectiveness.

Plant Roots↗

PubMed2024

Comparative genomic analysis and functional investigations for MCs catabolism mechanisms and evolutionary dynamics of MCs-degrading bacteria in ecology.

Microcystins (MCs) significantly threaten the ecosystem and public health. Biodegradation has emerged as a promising technology for removing MCs. Many MCs-degrading bacteria have been identified, including an indigenous bacterium Sphingopyxis sp. YF1 that could degrade MC-LR and Adda completely. Herein, we gained insight into the MCs biodegradation mechanisms and evolutionary dynamics of MCs-degrading bacteria, and revealed the toxic risks of the MCs degradation products. The biochemical characteristics and genetic repertoires of strain YF1 were explored. A comparative genomic analysis was performed on strain YF1 and six other MCs-degrading bacteria to investigate their functions. The degradation products were investigated, and the toxicity of the intermediates was analyzed through rigorous theoretical calculation. Strain YF1 might be a novel species that exhibited versatile substrate utilization capabilities. Many common genes and metabolic pathways were identified, shedding light on shared functions and catabolism in the MCs-degrading bacteria. The crucial genes involved in MCs catabolism mechanisms, including mlr and paa gene clusters, were identified successfully. These functional genes might experience horizontal gene transfer events, suggesting the evolutionary dynamics of these MCs-degrading bacteria in ecology. Moreover, the degradation products for MCs and Adda were summarized, and we found most of the intermediates exhibited lower toxicity to different organisms than the parent compound. These findings systematically revealed the MCs catabolism mechanisms and evolutionary dynamics of MCs-degrading bacteria. Consequently, this research contributed to the advancement of green biodegradation technology in aquatic ecology, which might protect human health from MCs.

Humans↗