Pseudomonas aeruginosa is a prevalent and pernicious pathogen equipped with extraordinary capabilities both to infect the host and to develop antimicrobial resistance (AMR). Monitoring the emergence of AMR high-risk clones and understanding the interplay of their pathogenicity and antibiotic resistance is of paramount importance to avoid resistance dissemination and to control P. aeruginosa infections. In this study, we report the identification of a multidrug-resistant (MDR) P. aeruginosa strain PA154197 isolated from a blood stream infection in Hong Kong. PA154197 belongs to a distinctive MLST550 clonal complex shared by two other international P. aeruginosa isolates VW0289 and AUS544. Comparative genome and transcriptome analysis of PA154197 with the reference strain PAO1 led to the identification of a variety of genetic variations in antibiotic resistance genes and the hyperexpression of three multidrug efflux pumps MexAB-OprM, MexEF-OprN, and MexGHI-OpmD in PA154197. Unexpectedly, the strain does not display a metabolic cost and a compromised virulence compared to PAO1. Characterizing its various physiological and virulence traits demonstrated that PA154197 produces a substantially higher level of the P. aeruginosa major virulence factor pyocyanin (PYO) than PAO1, but it produces a decreased level of pyoverdine and displays decreased biofilm formation compared with PAO1. Further analysis revealed that the secondary quorum-sensing (QS) system Pqs that primarily controls the PYO production is hyperactive in PA154197 independent of the master QS systems Las and Rhl. Together, these investigations disclose a unique, uncoupled QS mediated pathoadaptation mechanism in clinical P. aeruginosa which may account for the high pathogenic potentials and antibiotic resistance in the MDR isolate PA154197.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is one of the most used models for bacterial pathogenesis and successful infection requires its adaptation to the low oxygen environment in host gastrointestinal tracts. Central to this process is the Arc (aerobic respiratory control) two-component regulatory system that contains a sensor kinase ArcB and a response regulator ArcA. Nevertheless, a comprehensive profile of the ArcA regulon on the proteome level is still lacking in S. Typhimurium. Here we quantitatively profiled Salmonella proteome during anaerobiosis in an arcA-deleting mutant in comparison to its parental strain.In addition to known processes under its control, notably we found that ArcA represses ethanolamine utilization by directly binding to the promoter region of the eut operon.

Genomic studies revealed the glycoside hydrolases of family 48 (GH48) as a powerful marker for the identification of truly cellulolytic bacteria. Here we report an improved method for detecting cellulolytic bacteria in lab-scale biogas fermenters by using GH48 genes as a molecular marker in DNA and RNA samples. We developed a mixture of primers for the specific amplification of a GH48 gene region in a broad range of bacteria. Additionally, we built a manually curated reference database containing GH48 gene sequences directly linked to the corresponding taxonomic information. Phylogenetic correlation analysis of GH48 to 16S rRNA gene sequences revealed that GH48 gene sequences with 94% identity belong with high confidence to the same genus. Applying this analysis, GH48 amplicon reads revealed that at mesophilic fermenter conditions, 50–99% of the OTUs appear to belong to novel taxa. In contrast, at thermophilic conditions, GH48 gene sequences from the genus Hungateiclostridium dominated with 60–91% relative abundance. The novel primer combinations enabled detection and relative quantification of a wide spectrum of GH48 genes in cellulolytic microbial communities. Deep phylogenetic correlation analysis and a simplified taxonomic identification with the novel database facilitate identification of cellulolytic organisms, including the detection of novel taxa in biogas fermenters.

22Pseudomonas aeruginosa is a prevalent and pernicious pathogen equipped with both extraordinary 23 capabilities to infect the host and to develop antimicrobials resistance (AMR). Monitoring the 24 emergence of AMR high risk clones and understanding the interplay of their pathogenicity and 25 antibiotic resistance is of paramount importance to avoid resistance dissemination and to control 26 P. aeruginosa infections. In this study, we report the identification of a multidrug resistant (MDR) 27 P. aeruginosa strain PA154197 isolated from a blood stream infection in Hong Kong. PA154197 28 belongs to a distinctive MLST550 clonal complex shared by two international P. aeruginosa 29 isolates VW0289 and AUS544. Comparative genome and transcriptome analysis with the 30 reference strain PAO1 led to the identification of a variety of genetic variations in antibiotic 31 resistance genes and the hyper-expression of three multidrug efflux pumps MexAB-OprM, 32 MexEF-OprN, and MexGHI-OpmD in PA154197. Unlike many resistant isolates displaying an 33 attenuated virulence, PA154197 produces a significantly high level of the P. aeruginosa major 34 virulence factor pyocyanin (PYO) and displays an uncompromised virulence compared to PAO1. 35 Further analysis revealed that the secondary quorum sensing system Pqs which primarily controls 36 the PYO production is hyper-active in PA154197 independent of the master QS systems Las and 37 Rhl. Together, these investigations disclose a unique, uncoupled QS mediated pathoadaptation 38 mechanism in clinical P. aeruginosa which may account for the high pathogenic potentials and 39 antibiotics resistance in the MDR isolate PA154197. 40 41 Pseudomonas aeruginosa is a ubiquitous Gram-negative pathogen that causes a variety of 42 notorious infections in humans such as ventilator-associated pneumonia, lung infections of cystic 43 fibrosis (CF) patients, burn wound infection, and various sepsis syndromes. It is the second leading 44 cause of hospital-acquired infections and is especially problematic in ICUs, where it is the leading 45 cause of pneumonia among pediatric patients and is responsible for a large number of urinary tract 46 (10% in US and 19% in Europe), blood stream (3% in US and 10% in Europe), eye, ear, nose, and47 throat infections (1-3). Compounding the burden of these infections is the extraordinary capability 48 of the pathogen to develop antibiotic and multidrug resistance (MDR) even during the course of 49 antibiotics therapy. P. aeruginosa is one of the "ESKAPE" (Enterococcus spp., Staphylococcus 50 aureus, Klebsiella spp., Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter 51 spp.) organisms which are recognized by the WHO as an alarming threat to the global public heath 52 associated with antimicrobial resistance (AMR). As a consequence, the diseases outcome of the P. 53 aeruginosa infections is the complex interplay of the pathogen (its pathogenicity and virulence), 54 hospital environments (antibiotic therapies and the emergence of AMR), and the patie...

Bacteria must be able to cope with harsh environments to survive. In Gram-negative bacteria like Pseudomonas species, resistance-nodulation-division (RND) transporters contribute to this task by pumping toxic compounds out of cells. Previously, we found that the RND system TtgABC of Pseudomonas putida KT2440 confers resistance to toxic metal chelators of the bipyridyl group. Here, we report that the incubation of a ttgB mutant in medium containing 2,2’-bipyridyl generated revertant strains able to grow in the presence of this compound. This trait was related to alterations in the pp_2827 locus (homolog of mexS in Pseudomonas aeruginosa). The deletion and complementation of pp_2827 confirmed the importance of the locus for the revertant phenotype. Furthermore, alteration in the pp_2827 locus stimulated expression of the mexEF-oprN operon encoding an RND efflux pump. Deletion and complementation of mexF confirmed that the latter system can compensate the growth defect of the ttgB mutant in the presence of 2,2’-bipyridyl. To our knowledge, this is the first report on a role of pp_2827 (mexS) in the regulation of mexEF-oprN in P. putida KT2440. The results expand the information about the significance of MexEF-OprN in the stress response of P. putida KT2440 and the mechanisms for coping with bipyridyl toxicity.