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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
J L DaSilva, Jan Nguyen, Kevin P Fennelly, Adrian M Zelazny, Kenneth N Olivier
We used an amoeba model to study the intracellular growth and cytotoxicity of clinical strains of Mycobacteriumabscessus subsp. massiliense (Mabsm) isolated from 2 patients (one with cystic fibrosis, the other one with idiopathic bronchiectasis) during the early (smooth colonies) and late stage (rough colonies) of chronic pulmonary infection. Acanthamoeba castellanii were infected with Mabsm (MOI 100) and samples collected every 24 h for 72 h. Results showed Mabsm is able to survive in trophozoites and persist in cysts for at least 7 days...
October 19, 2017: Research in Microbiology
Bin Wang, Yangyong Lv, Xuejie Li, Yiying Lin, Hai Deng, Li Pan
The global regulator LaeA controls the production of many fungal secondary metabolites, possibly via chromatin remodeling. Here we aimed to survey the secondary metabolite profile regulated by LaeA in Aspergillus niger FGSC A1279 by genome sequencing and comparative transcriptomics between the laeA deletion (ΔlaeA) and overexpressing (OE-laeA) mutants. Genome sequencing revealed four putative polyketide synthase genes specific to FGSC A1279, suggesting that the corresponding polyketide compounds might be unique to FGSC A1279...
October 18, 2017: Research in Microbiology
Priyanka Chaudhary, Rajesh Kumar, Vivek Sagar, Subendu Sarkar, Rupneet Singh, Sujata Ghosh, Surjit Singh, Anuradha Chakraborti
Group A streptococcus (GAS) infection remains a major concern due to multiple diseases including pharyngitis, impetigo, acute rheumatic fever (ARF) and rheumatic heart disease (RHD). It uses different adhesins and virulence factors like Cpa (collagen binding protein) and Scl (collagen-like protein) in its pathogenicity. Scl having similarities with human collagen may contribute to inducing autoimmunity in the host. Here we assessed gene expression, antibody titer of Cpa, Scl1 and Scl2 in both clinical GAS isolates (n = 45) and blood (n = 45) obtained from pharyngitis, ARF (acute rheumatic fever) and RHD respectively...
September 30, 2017: Research in Microbiology
Alex Fiori Silva, Adriele Rodrigues Dos Santos, Daliah Alves Coelho Trevisan, Alessandra Braga Ribeiro, Paula Aline Zanetti Sá-Campanerut, Caroline Kukolj, Emanuel Maltempi de Souza, Rosilene Fressatti Cardoso, Terezinha Inez Estivalet Svidzinski, Benicio Alves de Abreu Filho, Miguel Machinski Junior, Jane Martha Graton Mikcha
The effect of cinnamaldehyde against biofilm cells of Salmonella Typhimurium ATCC 14028 was evaluated. We also assessed differential protein patterns that were expressed by biofilms compared with planktonic cells and protein expression by cinnamaldehyde-treated biofilms cells. This compound decreased biofilm biomass and metabolic activity of biofilms at both concentrations tested. Cinnamaldehyde treatment reduced the number of attached cells in polypropylene, reflected by colony count and scanning electron microscopy...
September 30, 2017: Research in Microbiology
Christopher J Law, Kamela O Alegre
Multidrug resistance is principally a consequence of the active transport of drugs out of the cell by proteins that are integral membrane transporters. In the following review, we present a synthesis of current understanding of the Escherichia coli multidrug resistance transporter, MdtM, a 410 amino acid residue protein that belongs to the large and ubiquitous major facilitator superfamily (MFS).
September 27, 2017: Research in Microbiology
Eliane H Yardeni, Elia Zomot, Eitan Bibi
MdfA is an interesting member of a large group of secondary multidrug (Mdr) transporters. Through genetic, biochemical and biophysical studies of MdfA, many challenging aspects of the multidrug transport phenomenon have been addressed. This includes its ability to interact with chemically unrelated drugs and how it utilizes energy to drive efflux of compounds that are not only structurally, but also electrically, different. Admittedly, however, despite all efforts and a recent pioneering structural contribution, several important mechanistic issues of the promiscuous capabilities of MdfA still seek better molecular and dynamic understanding...
September 23, 2017: Research in Microbiology
Yannick Colin, Jérôme Gury, Mathilde Monperrus, Sophie Gentes, Paola Ayala, Marisol Goni-Urriza, Rémy Guyoneaud
Mercury methylation and demethylation processes govern the fate of methylmercury in aquatic ecosystems. Under anoxic conditions, methylation activity is mainly of biological origin and is often the result of sulfate-reducing bacteria. In this study, use of a luminescent biosensor for screening methylmercury production was validated by exposing the reporter strain to methylating or non-methylating Desulfovibrio strains. The sensitivity of the biosensor to methylmercury was shown to depend on sulfate-reducing bacterial growth conditions...
September 23, 2017: Research in Microbiology
Mario Vaneechoutte
Lactobacillus iners is an unusual Lactobacillus species which does not grow on de Man Rogosa Sharpe agar, does not produce d-lactic acid, and only limited amounts of hydrogen peroxide. Its production of inerolysin, a cytotoxin, is also unusual for a lactobacillus. Epidemiological studies point to an ambiguous role for this species, which is quite often recovered in high numbers from vaginal dysbiosis and offers limited protection against vaginal dysbiosis and, subsequently, against sexually transmitted infections and adverse pregnancy outcome...
September 22, 2017: Research in Microbiology
Sonal Dharani, Dong Hyun Kim, Robert M Q Shanks, Yohei Doi, Daniel E Kadouri
The increase in multidrug-resistant Gram-negative bacterial infections has forced the reintroduction of antibiotics such as colistin. However, the spread of the plasmid-borne mcr-1 colistin resistance gene have moved us closer to an era of untreatable Gram-negative infections. To evaluate whether predatory bacteria could be used as a potential therapeutic to treat this upcoming threat, the ability of Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus to prey on several clinically relevant mcr-1-positive, colistin-resistant isolates was evaluated...
September 15, 2017: Research in Microbiology
Liliana M Ludueña, Maria S Anzuay, Cynthia Magallanes-Noguera, Maria L Tonelli, Fernando J Ibañez, Jorge G Angelini, Adriana Fabra, Matthew McIntosh, Tania Taurian
The mineral phosphate-solubilizing phenotype in bacteria is attributed predominantly to secretion of gluconic acid produced by oxidation of glucose by the glucose dehydrogenase enzyme and its cofactor, pyrroloquinoline quinone. This study analyzes pqqE gene expression and pqq promoter activity in the native phosphate-solubilizing bacterium Serratia sp S119 growing under P-limitation, and in the presence of root exudates obtained from peanut plants, also growing under P-limitation. Results indicated that Serratia sp...
October 2017: Research in Microbiology
Anumita Sarkar, Pallab Kumar Ghosh, Krishnendu Pramanik, Soumik Mitra, Tithi Soren, Sanjeev Pandey, Monohar Hossain Mondal, Tushar Kanti Maiti
Agricultural productivity is proven to be hampered by the synthesis of reactive oxygen species (ROS) and production of stress-induced ethylene under salinity stress. One-aminocyclopropane-1-carboxylic acid (ACC) is the direct precursor of ethylene synthesized by plants. Bacteria possessing ACC deaminase activity can use ACC as a nitrogen source preventing ethylene production. Several salt-tolerant bacterial strains displaying ACC deaminase activity were isolated from rice fields, and their plant growth-promoting (PGP) properties were determined...
September 9, 2017: Research in Microbiology
Shaomeng Wang, Fan Yang, Bin Yang
The post-transcriptional regulator CsrA regulates multiple unrelated processes such as central carbon metabolism, motility, biofilm formation and bacterial virulence in different bacteria. However, regulation by CsrA in enterohemorrhagic Escherichia coli (EHEC) O157:H7 is still largely unknown. In this study, we performed a detailed analysis of gene expression differences between the EHEC O157:H7 wild-type strain and a corresponding csrA::kan mutant using RNA-seq technology. Genes whose expression was affected by CsrA were identified and grouped into different clusters of orthologous group categories...
September 9, 2017: Research in Microbiology
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