SEARCH · PubMed Health
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.
It is argued that the average motility of bacterial populations should be identified with a diffusivity parameter. A simple capillary assay for quantifying this parameter is described, and some results obtained by using this procedure are presented. It is concluded that the assay combine speed and simplicity of operation with sufficient accuracy to make it a valuable tool in the assessment of motility.
Although the potential of microbial inoculants for sustainable agriculture and environmental restoration has been widely recognized, their field performance remains highly variable and often unpredictable. Current research and development frameworks for microbial inoculants primarily focus on their plant growth-promoting functions and metabolic traits, often overlooking the ecological processes that determine whether introduced strains can successfully disperse, access, and establish within the rhizosphere. Increasing evidence suggests that successful dispersal and establishment cannot be assumed in the highly heterogeneous conditions of soil systems. Here, we summarize the key mechanisms underlying bacterial motility and discuss its role within the broader framework of microbial dispersal, highlighting how motility-mediated processes contribute to rhizosphere colonization. We propose that bacterial motility represents a key mechanistic determinant of biofertilizer efficacy. Its role extends beyond the ability of inoculant strains to physically reach the rhizosphere, encompassing competitive colonization on the root surface, long-term persistence, and the ability to respond to dynamic root-derived chemical gradients associated with newly developing root tissues. We argue that inoculant motility should be elevated from a passive descriptive trait to a core design parameter that can be systematically incorporated and regulated during the development and optimization of microbial inoculants. We outline a multi-tiered strategic framework for next-generation biofertilizer engineering that integrates strain selection, community design, motility regulation, and deployment strategies, thereby unlocking the full potential of synthetic microbial consortia for sustainable agriculture, ecosystem restoration, and climate change mitigation.
It has been suggested that monitoring of uterine activity by placement of intrauterine catheters can cause an increase in maternal and fetal infection. The ways in which intrauterine catheters could transmit infection have been investigated. The risk of infection occurs primarily during placement of the catheter, although a risk also exists if bacterial nutrients are present in the fluid filling the catheter. Recommendations are made to minimize these risks.
Efficient and accurate identification of functional genes is critical to biological research, yet traditional single-species approaches are often limited by low efficiency. Previously, we established a novel method for identifying key genes using cross-species protein domain features and machine learning. However, the high multiplicity of gene members associated with specific domains creates a substantial workload for subsequent experimental validation. To address this, this study proposes an enhanced approach that integrates EggNOG-based protein sequence annotation with domain analysis. Unannotated sequences are subsequently analyzed for protein domains, generating a comprehensive "direct gene annotation plus domain" hybrid feature matrix. While the hybrid matrix model yielded comparable predictive accuracy, it significantly enhanced feature resolution: the top 50 predicted features were all known motility-related genes or domains. Furthermore, among the top 100 ranked features, 58 are confirmed to be directly related to motility based on experimental evidence. Although strict genus-level control still yielded 51 confirmed features, excessive taxonomic restriction drastically reduces the number of training genomes, which may paradoxically impair identification efficiency. These results demonstrate that the new method effectively reduces the subsequent experimental workload and enables high-throughput identification of functional genes in a single analysis. With accuracy and efficiency far exceeding those of existing single-species identification methods, it provides a highly efficient solution for mining key genes underlying other complex bacterial phenotypes.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
When assayed by a newly devised, simple and quantitative method, "motilometry", the motility of E. coli S-26 was found stimulated by cyclic adenosine 3':5'-monophosphate (cyclic AMP) and 8-hydroxy cyclic AMP as well as histamine, catecholamines and inhibited by cyclic guanosine 3':5'-monophosphate (cyclic GMP). The stimulation elicited by cyclic AMP or other biogenic amines was reversed by cyclic GMP. The experimental significance and implicaton of these findings are discussed.
Explore the source record for details and available documents.
Two companion papers in this series have characterized the interaction between Vibrio cholerae and the surfaces of eukaryotic cells. The present paper reports studies of the association between vibrios or Salmonella enteritidis and intact slices of intestinal tissue. A significant number of differences were noted in the characteristics of bacterial adhesion in these systems. The results are interpreted to indicate the presence of at least two receptors for vibrio adhesion on the mucosal surface of the rabbit small intestine. The receptor mediating the adhesion of salmonella appeared to be distinct from these. A primary role for bacterial motility in the process of adhesion of vibrios to mucosal surfaces could not be demonstrated in the assay systems studied. Rather, loss of motility in mutant vibrios appeared to be correlated with the simultaneous loss of adhesive factors (adhesins) from the bacterial surface. The inhibition of vibrio adhesion to slices of intestinal tissues by antibody to the heat-stable antigens of V. cholerae occurred in the absence of bacterial agglutination. Agglutination in this assay system appeared to be an artifact in that it could be observed only in experiments where extremely high concentrations of vibrios were used. We speculate that such high vibrio concentrations are not likely to be present in humans at the time of infection and that agglutination in the lumen of the intestine might therefore play only a minor role in prophylactic immunity against natural cholera and other enteric infections of humans.
Pseudomonas aeruginosa is a major opportunistic pathogen, and its laboratory reference strain, PAO1, is widely used in microbiological and genetic studies. However, PAO1 often exhibits phenotypic variability that can affect experimental reproducibility. Our PAO1 stock, obtained from a public biobank, is resistant to PP7, a pilus-dependent single-stranded RNA phage known to infect PAO1. This suggests the presence of genetic variants in the stock. To check this possibility, we isolated six phenotypically distinct variants (GU1-GU6) and performed genomic and phenotypic analyses. Notable differences were observed among the isolates in terms of motility, pyocyanin production, and susceptibility to PP7. Whole-genome sequencing revealed that four of the six variants harbored mutations in pilus-associated genes. Among these, GU3 carried a mutation in pilT, which encodes a motor protein essential for type IV pilus retraction, and the loss of retraction led to the PP7 resistance. GU2, GU4, and GU6 shared a nonsense mutation in pilJ, a gene involved in chemotaxis and pilus extension, resulting in reduced twitching motility and lower PP7 infection efficiency. Additionally, we found that a mutation in lasR, a master regulator of quorum sensing, promoted the replication of prophage Pf6, which was integrated into the PAO1 genome. Pf6 replication interferes with PP7 infection, providing an alternative mechanism of resistance. These findings offer new insights into the complexity of phage-host interactions and emphasize the importance of routine verification and careful handling of P. aeruginosa sublines used in bacteriological and phage research.IMPORTANCEPhenotypic and genotypic variability in Pseudomonas aeruginosa PAO1 has been widely reported, raising concerns regarding the reproducibility of laboratory studies that rely on this reference strain. In this study, we isolated six PAO1 variants from a single laboratory stock and demonstrated that they differed markedly in motility, pyocyanin production, and susceptibility to the ssRNA phage PP7. Whole-genome sequencing has revealed that even a single mutation in a pilus-associated gene can profoundly affect bacterial motility and phage susceptibility. Furthermore, we showed that a mutation in lasR, a key regulator of the quorum-sensing system, triggered replication of the Pf6 prophage, which in turn hindered PP7 infection. These findings underscore the dynamic nature of laboratory strains and highlight the need for caution when interpreting results from phage-host interaction studies using reference strains. Our results provide a new understanding of how subtle genetic changes in model strains influence experimental outcomes in microbiology.
The widespread dissemination of multidrug-resistant (MDR) E. coli has led to a decrease in the efficacy of antibiotics, posing severe challenges to clinical anti-infective therapy. Owing to their safety, multitarget activities, and low risk of inducing drug resistance, plant polysaccharides represent a promising alternative strategy. In this study, an acidic polysaccharide (IVP-3) was isolated and purified from the medicinal and edible plant Illicium verum, and it was found to inhibit MDR E. coli colonization by disrupting its biofilm. The Mw of IVP-3 was determined to be 35.566 kDa. Its backbone consists of →4)-α-D-GalpA-6-OMe-(1→, →4)-α-D-GalpA-(1→, →4)-β-D-Galp-(1→, and →3,4)-α-D-GalpA-(1 → residues, whereas the branched chain is composed of α-L-Araf-(1 → 5)-α-L-Araf-(1 → attached to the O-5 position of →2,5)-α-L-Araf-(1→, which is further linked to the O-3 position of the backbone. Mechanistically, IVP-3 disrupts the structure of fimbriae and flagella, inhibits bacterial motility, effectively prevents initial biofilm adhesion, and eradicates preformed mature biofilms. Additionally, IVP-3 damages cell membrane integrity, disrupts the proton motive force, and induces energy metabolism disorder, efflux pump inhibition, and oxidative stress, ultimately leading to bacterial lysis. This study provides a theoretical basis for the development of natural antibacterial agents targeting MDR E. coli biofilms and for the high-value utilization of Illicium verum.
In a sensitive strain of Bacillus thuringiensis (Berliner), aflatoxin B1 inhibited growth with a dose above 5.0 microgram/ml. With subinhibitory levels (0.5 - 5.0 microgram/ml) physiological damage (decreased growth rate) and cellular alteration (filamentous cells) were noted. With these doses the mycotoxin disturbs various metabolisms : DNA synthesis (gradual blockage of the specific bacteriophage multiplication and dispersion of nuclear apparatus in giant cells); protein synthesis (decrease of protease secretion (2.0 microgram/ml), thuricin excretion (3.0 microgram/ml) and inhibition of endotoxin formation (4.0 microgram/ml); specific activities (bacterial motility, flagellar arrangment and sporulation were respectively affected with 1.0, 0.5 and 4.0 microgram/ml). The mycotoxin did not affect the metabolism of a resistant mutant isolated in the presence of a lethal dose of aflatoxin B1 (mutation rate : 1.10(8) with 20 microgram/ml). The numerous bacterial responses to aflatoxin B1 indicate that the probable site of its toxic binding may not be restricted to a particular locus on the DNA. On the contrary these observations suggest that there exist many combining affinities of the mycotoxin for intracellular sites or interference with a key-function such as the messenger-RNA synthesis.
Photon correlation spectroscopy is shown to be a practical technique for the accurate determination of translational speeds of bacteria. Though other attempts have been made to use light scattering as a probe of various aspects of bacterial motility, no other comprehensive studies to establish firmly the basic capabilities and limitations of the technique have been published. The intrinsic accuracy of the assay of translational speeds by photon correlation spectroscopy is investigated by analysis of synthetic autocorrelation data; consistently accurate estimates of the mean and second moment of the speed distribution can be calculated. Extensive analyses of experimental preparations of Salmonella typhimurium examine the possible sources of experimental difficulty with the assay. Cinematography confirms the bacterial speed estimates obtained by photon correlation techniques.
Details are presented for the construction of a simple precision temperature-controlled chamber for investigating bacterial motile behavior. Independent of original incubation temperature, all species of motile bacteria observed showed a five- to sevenfold increase in average translational velocity (micrometers per second) as the environment temperature was incremented over the range from 10 to 50 degrees C. Temperature jumps downward produced transient tumbling or reciprocal behavior responses, depending on the mode of flagellar distribution, in all species examined. Upward temperature jumps induced accelerated velocities without tumbling or reversal. A partial capacity adaptation to temperature was noted, in that the greatest average translational velocity at any given observation temperature occurred when the organisms were grown at temperatures less than the optimum.
Two novel aerobic, rod-shaped, motile bacterial strains, designated as sgz302134T and sgz301742T, were isolated from paddy soil in Fujian Province. Strains sgz302134T and sgz301742T shared the highest 16S rRNA gene sequence similarities with the type strains Azospirillum isscasi C340-1T (98.2%) and Azospirillum thiophilum DSM 21654T (97.4%), respectively. The phylogenetic tree based on 16S rRNA gene sequences showed that two strains clustered with members of the genus Azospirillum. Growth of strains sgz302134T and sgz301742T was observed at 10-45 °C, pH 5.0-9.5 and 0-0.5% (w/v) NaCl and 15-37 °C, pH 6.0-9.0 and 0-1.0% (w/v) NaCl, respectively. Strains sgz302134T and sgz301742T contained Q-10 as the main quinone. The main fatty acids (>10%) of both strains were summed feature 2 (C12 : 0 aldehyde), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and C16 : 0. The genomic DNA G+C content of strains sgz302134T and sgz301742T was 68.4 and 68.3%, respectively. The digital DNA-DNA hybridization and average nucleotide identity values between the two strains and their related reference strains were 27.8 and 87.4% and 22.0 and 84.3%, respectively. Both strains possessed nif genes nifBDEHKN. Based on the above results, these two strains represent two novel species of the genus Azospirillum, for which the names Azospirillum mesophilum sp. nov. and Azospirillum terrae sp. nov. are proposed. The type strains are sgz302134T (=MCCC 1K09520T=KCTC 8840T) and sgz301742T (=MCCC 1K09804T=KCTC 18149T), respectively.
The number of bacteria retained by agar dipslides immersed in bacterial suspensions was dependent solely on suspension population density and was unaffected by the nutrient status of the agar surface or liquid, disturbance of the liquid, or bacterial motility and chemotaxis.
The previous demonstration that sperm kept at body temperature (37 degrees C) had a marked deterioration in motility accompanied by an overgrowth of bacteria in the semen and a concomitant decrease in pH led to this study to test the hypothesis that the decrease in motility was caused by the bacteria or by bacterial alteration of seminal pH. Semen specimens from fertile prevasectomy patients with and without added antibiotics were maintained at 20 degrees C and 37 degrees C and evaluated at 3, 12, and 18 hours after collection. There was still a significant deterioration in spermatozoal motility in the samples kept at 37 degrees C even when bacterial growth and change in pH were prevented by buffered antibiotics. Although the decrease in spermatozoal motility at body temperature may in part be attributed to bacterial growth or the products of bacterial metabolism, clearly another factor is present related to time and temperature and independent of the presence of bacteria.
A new defect of chemotaxis and random motility of polymorphonuclear leukocytes is described in a patient with severe recurrent bacterial infections since early childhood. This defect seems to be intrinsic to the cells. The patient's plasma did not contain an inhibitor of chemotaxis. Addition of plasma to the patient's cells restored their chemotactic activity. High concentrations of immunoglobulin E were found in the patient's plasma. Phagocytosis, bacterial killing, and reduction of nitroblue tetrazolium salt were normal. Histological examination of lung tissue revealed a pattern similar to that observed in chronic granulomatous disease.