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Research in Microbiology

Helen I Zgurskaya, Valentin V Rybenkov, Ganesh Krishnamoorthy, Inga V Leus
Antibiotic resistance is a serious threat to public health. Significant efforts are currently directed toward containment of the spread of resistance, finding new therapeutic options concerning resistant human and animal pathogens, and addressing the gaps in the fundamental understanding of mechanisms of resistance. Experimental data and kinetic modeling revealed a major factor in resistance, the synergy between active efflux and the low permeability barrier of the outer membrane, which dramatically reduces the intracellular accumulation of many antibiotics...
February 15, 2018: Research in Microbiology
Lacey L Westphal, Jasmine Lau, Zuly Negro, Ivan J Moreno, Wazim Ismail Mohammed, Heewook Lee, Haixu Tang, Steven E Finkel, Karin E Kram
Experimental evolution studies have characterized the genetic strategies microbes utilize to adapt to their environments, mainly focusing on how microbes adapt to constant and/or defined environments. Using a system that incubates Escherichia coli in different complex media in long-term batch culture, we have focused on how heterogeneity and environment affects adaptive landscapes. In this system, there is no passaging of cells, and therefore genetic diversity is lost only through negative selection, without the experimentally-imposed bottlenecking common in other platforms...
February 14, 2018: Research in Microbiology
Yi-Ling Lo, Chyi-Liang Chen, Lunda Shen, Ying-Ching Chen, Yi-Hsin Wang, Chung-Chan Lee, Lian-Chen Wang, Chih-Hsien Chuang, Rajendra Prasad Janapatla, Cheng-Hsun Chiu, Hwan-You Chang
FliA is known to be a sigma factor that regulates bacterial flagella gene expression. Accumulating evidence suggests that FliA is involved in bacterial behavior other than motility. To elucidate the contribution of FliA to Pseudomonas aeruginosa pathophysiology, we analyzed the biological properties and gene expression profiles of a ΔfliA mutant. Transcriptome analysis results demonstrated that the expression levels of flagella biogenesis genes decreased dramatically in the mutant; consequently, the ΔfliA mutant failed to synthesize flagella and exhibited reduced motility...
February 9, 2018: Research in Microbiology
Timothy Travers, Katherine J Wang, Cesar A López, S Gnanakaran
Gram-negative multidrug resistance currently presents a serious threat to public health with infections effectively rendered untreatable. Multiple molecular mechanisms exist that cause antibiotic resistance and in addition, the last three decades have seen slowing rates of new drug development. In this review, we summarize the use of various computational techniques for investigating the mechanisms of multidrug resistance mediated by Gram-negative tripartite efflux pumps and membranes. Recent work in our lab combines data-driven sequence and structure analyses to study the interactions and dynamics of these bacterial components...
February 8, 2018: Research in Microbiology
Qing Li, Zunfeng Li, Xingxing Li, Liming Xia, Xuan Zhou, Zhihui Xu, Jiahui Shao, Qirong Shen, Ruifu Zhang
Bacillus velezensis strain SQR9 is a well-investigated rhizobacterium with an outstanding ability to colonize roots, enhance plant growth and suppress soil-borne diseases. The recognition that biofilm formation by plant-beneficial bacteria is crucial for their root colonization and function has resulted in increased interest in understanding molecular mechanisms related to biofilm formation. Here, we report that the gene ftsE, encoding the ATP-binding protein of an FtsEX ABC transporter, is required for efficient SQR9 biofilm formation...
February 7, 2018: Research in Microbiology
Karl A Hassan, Qi Liu, Liam D H Elbourne, Irshad Ahmad, David Sharples, Varsha Naidu, Chak Lam Chan, Liping Li, Steven P D Harborne, Alaska Pokhrel, Vincent L G Postis, Adrian Goldman, Peter J F Henderson, Ian T Paulsen
The proteobacterial antimicrobial compound efflux (PACE) family of transport proteins was only recently described. PACE family transport proteins can confer resistance to a range of biocides used as disinfectants and antiseptics, and are encoded by many important Gram-negative human pathogens. However, we are only just beginning to appreciate the range of functions and the mechanism(s) of transport operating in these proteins. Genes encoding PACE family proteins are typically conserved in the core genomes of bacterial species rather than on recently acquired mobile genetic elements, suggesting that they confer important core functions in addition to biocide resistance...
February 1, 2018: Research in Microbiology
Katerina Bogdanova, Magdalena Röderova, Milan Kolar, Katerina Langova, Martin Dusek, Petr Jost, Klara Kubelkova, Pavel Bostik, Jana Olsovska
Bacterial biofilms pose a serious medical problem due to their significant resistance to antimicrobials, and staphylococci are recognized as the most frequent cause of biofilm-associated infections. The hop plant (Humulus lupulus L.) contains substances that have been determined to act as anti-infective agents against bacteria, mainly in planktonic form. Therefore, we decided to investigate the antibiofilm properties of Humulus lupulus L.-derived compounds (humulone, lupulone and xanthohumol) against a selected group of Staphylococcus spp...
January 30, 2018: Research in Microbiology
Attilio Vittorio Vargiu, Venkata Krishnan Ramaswamy, Giuliano Malloci, Ivana Malvacio, Alessio Atzori, Paolo Ruggerone
The putative mechanism by which bacterial RND-type multidrug efflux pumps recognize and transport their substrates is a complex and fascinating enigma of structural biology. How a single protein can recognize a huge number of unrelated compounds and transport them through one or just a few mechanisms is an amazing feature not yet completely unveiled. The appearance of cooperativity further complicates the understanding of structure-dynamics-activity relationships in these complex machineries. Experimental techniques may have limited access to the molecular determinants and to the energetics of key processes regulating the activity of these pumps...
January 30, 2018: Research in Microbiology
Xiaolin Wang, Xuelian Cao, Shunming Li, Qianting Ou, Dongxin Lin, Zhenjiang Yao, Sidong Chen, Chuan'an Wu, Guoming Wen, Xiaohua Ye
Streptococcus agalactiae (GBS) remains a major cause of invasive infections in neonates and pregnant women. Our aim was to evaluate the phenotypic and molecular characteristics of GBS isolates in order to reveal potential relationships among molecular characteristics and differences in genotype-phenotype characteristics between ST17 and ST19. A total of 104 GBS isolates were collected from pregnant women. All isolates were tested for antibiotic susceptibility by disk diffusion method and molecular characteristics, including antibiotic-resistant genes, virulence genes, serotypes and STs...
January 26, 2018: Research in Microbiology
Yimin Hu, Quanxin Cai, Shen Tian, Yong Ge, Zhiming Yuan, Xiaomin Hu
DegS and DegU make up a two component system belonging to a class of signal transduction systems that play important roles in a broad range of bacterial responses to the environment. However, little study has been done to explore the physiological functions of DegS-DegU in mosquitocidal Lysinibacillus sphaericus. In this study, it was found that deletion of degU or degS-degU inhibited the swarming motility, biofilm formation, sporulation and binary toxin production through regulating the related genes, and phosphorylation was necessary for the functions of DegU...
January 25, 2018: Research in Microbiology
Birte Vester
The Cfr methyl transferase causes an RNA methylation of the bacterial ribosomes impeding reduced or abolished binding of many antibiotics acting at the peptidyl transferase centre. It provides multi-resistance to eight classes of antibiotics, most of which are in clinical and veterinary use. The cfr gene is found in various bacteria in many geographical locations and placed on plasmids or associated with transposons. Cfr-related genes providing similar resistance have been identified in Bacillales, and now also in the pathogens Clostridium difficile and Enterococcus faecium...
January 25, 2018: Research in Microbiology
Tristan Lurthy, Nicole Alloisio, Pascale Fournier, Stéphanie Anchisi, Alise Ponsero, Philippe Normand, Petar Pujic, Hasna Boubakri
The transcriptome of Frankia alni strain ACN14a was compared between in vitro ammonium-replete (N-replete) and ammonium-free dinitrogen-fixing (N-fixing) conditions using DNA arrays. A Welch-test (p < 0.05) revealed significant upregulation of 252 genes under N-fixing vs. N-replete (fold-change (FC) ≥ 2), as well as significant downregulation of 48 other genes (FC ≤ 0.5). Interestingly, there were 104 Frankia genes upregulated in vitro that were also significantly upregulated in symbiosis with Alnus glutinosa, while the other 148 genes were not, showing that the physiology of in vitro fixation is markedly different from that under symbiotic conditions...
January 25, 2018: Research in Microbiology
Dhenesh Puvanendran, Quentin Cece, Martin Picard
Efflux pumps are systems devoted to the extrusion of noxious compounds. In this review, we discuss the various strategies that have thus far been undertaken for the investigation of efflux pumps after reconstitution into liposomes. It is challenging to uncover mechanisms and dynamics of efflux pumps due to a number of characteristics: their function depends on the correct assembly of three components and they span two adjacent membranes whose lipid compositions are very different. In addition, efflux pumps are active transporters that need energy to work...
December 4, 2017: Research in Microbiology
Muriel Masi, Estelle Dumont, Julia Vergalli, Jelena Pajovic, Matthieu Réfrégiers, Jean-Marie Pagès
To understand antibiotic resistance in Gram-negative bacteria, a key point is to investigate antibiotic accumulation, which is defined by influx and efflux. Several methods exist to evaluate membrane permeability and efflux pump activity, but they present disadvantages and limitations. An optimized spectrofluorimetric method using intrinsic tryptophan fluorescence as an internal standard, as well as a complementary microfluorimetric assay following time-course accumulation in intact individual cells, have been developed...
December 2, 2017: Research in Microbiology
Marta Castrillo, Eva M Luque, Javier Pardo-Medina, M Carmen Limón, Luis M Corrochano, Javier Avalos
Stimulation by light of carotenoid biosynthesis in the mycelia of the fungus Neurospora crassa starts with transient transcriptional induction of the structural genes of the pathway triggered by the White Collar photoreceptor complex. Most studies on this process were carried out under standard growth conditions, but photoinduced carotenoid accumulation is more efficient if the fungus is incubated at low temperatures, from 6 to 12°C. We have investigated the transcriptional photoresponse at 8°C of the genes for proteins that participate in the carotenoid pathway...
December 1, 2017: Research in Microbiology
Ariane Toussaint, Frédérique Van Gijsegem
Mu-like transposable phages and prophages have been isolated from, or predicted, in a wide range of bacterial phyla. However, related B3-like transposable phages, which differ in their genome organisation and the DDE transposase and transposition activator they code for have thus far been restricted to a very limited set of hosts. Through sequence similarity searches, we have now expanded the number of predicted B3-like prophages and uncovered a third genomic organisation. These new genomes, although only prophages, further illustrate the previously reported mosaicism existing in the proposed "Saltoviridae" family of Caudovirales, and further support the proposal to move morphology criteria (contractile vs...
November 17, 2017: Research in Microbiology
Zachary Aron, Timothy J Opperman
Resistance-nodulation-division (RND) superfamily efflux pumps play a major role in multidrug resistance (MDR) of Gram-negative pathogens by extruding diverse classes of antibiotics from the cell. There has been considerable interest in developing efflux pump inhibitors (EPIs) of RND pumps as adjunctive therapies. The primary challenge in EPI discovery has been the highly hydrophobic, poly-specific substrate binding site of the target. Recent findings have identified the hydrophobic trap, a narrow phenylalanine-lined groove in the substrate-binding site, as the "Achilles heel" of the RND efflux pumps...
November 13, 2017: Research in Microbiology
Natasha Weston, Prateek Sharma, Vito Ricci, Laura J V Piddock
Bacterial multidrug efflux systems are a major mechanism of antimicrobial resistance and are fundamental to the physiology of Gram-negative bacteria. The resistance-nodulation-division (RND) family of efflux pumps is the most clinically significant, as it is associated with multidrug resistance. Expression of efflux systems is subject to multiple levels of regulation, involving local and global transcriptional regulation as well as post-transcriptional and post-translational regulation. The best-characterised RND system is AcrAB-TolC, which is present in Enterobacteriaceae...
November 8, 2017: Research in Microbiology
Song-Tao Zhang, Xiao-Ning Song, Ning Li, Ke Zhang, Guo-Shun Liu, Xue-Dong Li, Zhi-Zhong Wang, Xiao-Bing He, Guo-Feng Wang, Hui-Fang Shao
Soil microorganisms play a crucial role in cycling soil nutrients and providing organic nutrients for plant growth and development. Fertilisation balances soil fertility and quality, and affects soil microbial communities. Fertilisation is a frontier subject in agricultural and environmental sciences. Here we showed that the application of high-carbon basal fertiliser treatment could improve the tobacco yield and quality when compared to chemical fertiliser, high-carbon basal fertiliser and mixed high-carbon chemical fertiliser...
November 7, 2017: Research in Microbiology
Bassam A Elgamoudi, Julian M Ketley
In this study, a LOV-based fluorescent reporter (light, oxygen, or voltage-sensing domains of phototropin), termed iLOV, was adapted for Campylobacter jejuni and used to investigate promoter activity via monitoring fluorescence intensity and to study the localisation of two chemotaxis proteins. The pC46 complementation vector contains coding sequence from cj0046, a C. jejuni NCTC11168 pseudo-gene and is used to integrate cloned genes onto the C. jejuni chromosome. The pC46 vector was used to construct plasmids containing iLOV, driven by three different C...
November 4, 2017: Research in Microbiology
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