Physiological Effects of TolC-Dependent Multidrug Efflux Pumps in Escherichia coli: Impact on Motility and Growth Under Stress Conditions.

Enterobacteriaceae possess eight TolC-dependent multidrug efflux pumps: AcrAB-TolC, AcrAD-TolC, AcrEF-TolC, MdtEF-TolC, MdtABC-TolC, EmrAB-TolC, EmrYK-TolC, and MacAB-TolC, which efflux bile salts, antibiotics, metabolites, or other compounds. However, our understanding of their physiological roles remains limited, especially for less-studied pumps like EmrYK-TolC. In this study, we tested the effects on swimming motility and growth under stress conditions of Escherichia coli mutants individually deleted for each inner-membrane transporter component of all eight TolC-dependent pumps, a mutant deleted for the AcrB-accessory protein AcrZ, and a mutant simultaneously deleted for all eight pumps (ΔtolC).

Resistance to carbapenems in the urban soil isolate Cupriavidus taiwanensis S2-1-W is associated with OXA-1206, a newly discovered carbapenemase.

Aims: Cupriavidus isolates are found in environmental and clinical samples and are often resistant to carbapenems, which are last-resort antibiotics. However, their carbapenem-resistance molecular mechanisms remain unknown. This study aimed to (i) characterize and sequence the carbapenem-resistant soil isolate Cupriavidus taiwanensis S2-1-W to uncover its antibiotic resistance determinants; and (ii) clone and characterize a putative novel carbapenemase gene identified in this isolate.

First report of a carbapenem-resistant Aeromonas veronii environmental isolate in the United States co-harboring two carbapenemase genes.

Objectives: The spread of carbapenem-resistant bacteria (CRB), and especially carbapenemase-producing CRB, is a global public health threat. Among them, Aeromonas species are of increasing concern because these emerging opportunistic pathogens are widespread in the environment and have increasingly been found to be resistant to carbapenems. The aim of this study was to investigate the genome and carbapenem-resistance determinants of Aeromonas veronii SS-M2-3, a highly carbapenem-resistant, carbapenemase-producing, river isolate from California (U.

Freshwater and Marine Environments in California Are a Reservoir of Carbapenem-Resistant Bacteria.

Carbapenems are last-resort antibiotics used to treat multidrug-resistant bacterial infections. Resistance to carbapenems has been designated as an urgent threat and is increasing in healthcare settings. However, little is still known about the distribution and characteristics of carbapenem-resistant bacteria (CRB) outside of healthcare settings.

The multidrug efflux pump regulator AcrR directly represses motility in .

Efflux and motility are two key biological functions in bacteria. Recent findings have shown that efflux impacts flagellum biosynthesis and motility in and other bacteria. AcrR is known to be the major transcriptional repressor of AcrAB-TolC, the main multidrug efflux pump in and other .

Sodium Malonate Inhibits the AcrAB-TolC Multidrug Efflux Pump of and Increases Antibiotic Efficacy.

There is an urgent need to find novel treatments for combating multidrug-resistant bacteria. Multidrug efflux pumps that expel antibiotics out of cells are major contributors to this problem. Therefore, using efflux pump inhibitors (EPIs) is a promising strategy to increase antibiotic efficacy.

The Multidrug Efflux Regulator AcrR of Escherichia coli Responds to Exogenous and Endogenous Ligands To Regulate Efflux and Detoxification.

The transcriptional repressor AcrR is the main regulator of the multidrug efflux pump AcrAB-TolC, which plays a major role in antibiotic resistance and cell physiology in Escherichia coli and other . However, it remains unknown which ligands control the function of AcrR. To address this gap in knowledge, this study tested whether exogenous and/or endogenous molecules identified as potential AcrR ligands regulate the activity of AcrR.

Urban and agricultural soils in Southern California are a reservoir of carbapenem-resistant bacteria.

Carbapenems are last-resort β-lactam antibiotics used in healthcare facilities to treat multidrug-resistant infections. Thus, most studies on identifying and characterizing carbapenem-resistant bacteria (CRB) have focused on clinical settings. Relatively, little is still known about the distribution and characteristics of CRBs in the environment, and the role of soil as a potential reservoir of CRB in the United States remains unknown.

Single-molecule detection of cancer mutations using a novel PCR-LDR-qPCR assay.

Detection of low-abundance mutations in cell-free DNA is being used to identify early cancer and early cancer recurrence. Here, we report a new PCR-LDR-qPCR assay capable of detecting point mutations at a single-molecule resolution in the presence of an excess of wild-type DNA. Major features of the assay include selective amplification and detection of mutant DNA employing multiple nested primer-binding regions as well as wild-type sequence blocking oligonucleotides, prevention of carryover contamination, spatial sample dilution, and detection of multiple mutations in the same position.

Comparative Genomics Reveals a Well-Conserved Intrinsic Resistome in the Emerging Multidrug-Resistant Pathogen Cupriavidus gilardii.

The Gram-negative bacterium is an emerging multidrug-resistant pathogen found in many environments. However, little is known about this species or its antibiotic resistance mechanisms. We used biochemical tests, antibiotic susceptibility experiments, and whole-genome sequencing to characterize an environmental isolate.

Prevalence and characterization of carbapenem-resistant bacteria in water bodies in the Los Angeles-Southern California area.

Carbapenems are β-lactam antibiotics used in healthcare settings as last resort drugs to treat infections caused by antibiotic-resistant bacteria. Carbapenem-resistant bacteria are increasingly being isolated from healthcare facilities; however, little is known about their distribution or prevalence in the environment, especially in the United States, where their distribution in water environments from the West Coast has not been studied before. The aim of this study was to determine the prevalence of carbapenem-resistant bacteria and carbapenemase genes in water bodies from the Los Angeles area (California, USA).

Regulation of acrAB expression by cellular metabolites in Escherichia coli.

Objectives: Multidrug efflux pumps mediate resistance to antibiotics and other toxic compounds. We studied the role of AcrAB-TolC, the main efflux pump in Escherichia coli, in regulating gene expression.

Methods: Deletion mutants, an acrABp-lacZ fusion and reverse transcription-real-time quantitative PCR experiments were used to study the role of AcrAB-TolC and metabolism in regulating gene expression of the acrAB operon and its transcriptional regulators.

Many chromosomal genes modulate MarA-mediated multidrug resistance in Escherichia coli.

Multidrug resistance (MDR) in clinical isolates of Escherichia coli can be associated with overexpression of marA, a transcription factor that upregulates multidrug efflux and downregulates membrane permeability. Using random transposome mutagenesis, we found that many chromosomal genes and environmental stimuli affected MarA-mediated antibiotic resistance. Seven genes affected resistance mediated by MarA in an antibiotic-specific way; these were mostly genes encoding unrelated enzymes, transporters, and unknown proteins.

Role of the multidrug resistance regulator MarA in global regulation of the hdeAB acid resistance operon in Escherichia coli.

MarA, a transcriptional regulator in Escherichia coli, affects functions such as multiple-antibiotic resistance (Mar) and virulence. Usually an activator, MarA is a repressor of hdeAB and other acid resistance genes. We found that, in wild-type cells grown in LB medium at pH 7.

Helicobacter pylori EstV: identification, cloning, and characterization of the first lipase isolated from an epsilon-proteobacterium.

Bacterial lipases are attracting an enormous amount of attention due to their wide biotechnological applications and due to their roles as virulence factors in some bacteria. Helicobacter pylori is a significant and widespread pathogen which produces a lipase(s) and phospholipases that seem to play a role in mucus degradation and the release of proinflammatory and cytotoxic compounds. However, no H.

Identification of a carboxylesterase-producing Rhodococcus soil isolate.

Subtropical soil microbial isolates were screened for carbohydrate, tributyrin, or olive oil hydrolysis using agar plates supplemented with the corresponding substrates. A heterotrophic, aerobic, Gram-positive strain displaying activity on tributyrin was selected and further characterized. Analysis of the morphological and physiological traits of the strain placed it as a member of the genus Rhodococcus.

Activation and inhibition of Candida rugosa and Bacillus-related lipases by saturated fatty acids, evaluated by a new colorimetric microassay.

Research on lipase inhibitors could help in the therapy of diseases caused by lipase-producing microorganisms and in the design of novel lipase substrate specificities for biotechnology. Here we report a fast and sensitive colorimetric microassay that is low-cost and suitable for high-throughput experiments for the evaluation of lipase activity and inhibition. Comparison of Candida rugosa activity and inhibition with previous HPLC results validated the method, and revealed the importance of the reaction mixture composition.

Analysis of Bacillus megaterium lipolytic system and cloning of LipA, a novel subfamily I.4 bacterial lipase.

The lipolytic system of Bacillus megaterium 370 was investigated, showing the existence of at least two secreted lipases and a cell-bound esterase. A gene coding for an extracellular lipase was isolated and cloned in Escherichia coli. The cloned enzyme displayed high activity on short to medium chain length (C(4)-C(8)) substrates, and poor activity on C(18) substrates.