From acids to osmZ: multiple factors influence synthesis of the OmpF and OmpC porins in Escherichia coli

Author: Pratt, L.A.; Hsing, W.; Gibson, K.E.; Silhavy, T.J. Description: In Escherichia coli, levels of the two major outer membrane porin proteins, OmpF and OmpC, are regulated in response to a variety of environmental parameters, and numerous factors have been shown to influence porin synthesis. EnvZ and OmpR control porin-gene transcription in response to osmolarity, and the antisense RNA, MicF, influences ompF translation. In contrast to these characterized factors, some of the components reported to influence porin expression have only modest effects and/or act indirectly. For others, potential regulatory roles,…

See more and a link to full text

Urinary tract infections: epidemiology, mechanisms of infection and treatment options

Author: Flores-Mireles, A.L.; Walker, J.N.; Caparon, M.; Hultgren, S.J. Description: Urinary tract infections (UTIs) are a severe public health problem and are caused by a range of pathogens, but most commonly by Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis and Staphylococcus saprophyticus. High recurrence rates and increasing antimicrobial resistance among uropathogens threaten to greatly increase the economic burden of these infections. In this Review, we discuss how basic science studies are elucidating the molecular details of the crosstalk that occurs at the host-pathogen interface, as well as the consequences…

See more and a link to full text

Interplay between iron homeostasis and virulence: Fur and RyhB as major regulators of bacterial pathogenicity

Author: Porcheron, Gaelle; Dozois, Charles M. Description: In bacteria-host interactions, competition for iron is critical for the outcome of the infection. As a result of its redox properties, this metal is essential for the growth and proliferation of most living organisms, including pathogenic bacteria. This metal is also potentially toxic, making the precise maintenance of iron homeostasis necessary for survival. Iron acquisition and storage control is mediated in most bacteria by the global ferric uptake regulator (Fur) and iron-responsive small regulatory non-coding RNAs (RyhB in the model organism Escherichia coli)….

See more and a link to full text

Single-molecule imaging of FtsK translocation reveals mechanistic features of protein-protein collisions on DNA

Author: Lee, Ja Yil; Finkelstein, Ilya J.; Arciszewska, Lidia K.; Sherratt, David J.; Greene, Eric C. Description: In physiological settings, DNA translocases will encounter DNA-bound proteins, which must be dislodged or bypassed to allow continued translocation. FtsK is a bacterial translocase that promotes chromosome dimer resolution and decatenation by activating XerCD-dif recombination. To better understand how translocases act in crowded environments, we used single-molecule imaging to visualize FtsK in real time as it collided with other proteins. We show that FtsK can push, evict, and even bypass DNA-bound proteins. The…

See more and a link to full text

Microplastic pollution increases gene exchange in aquatic ecosystems

Author: Arias-Andres, Maria; Klumper, Uli; Rojas-Jimenez, Keilor; Grossart, Hans-Peter Description: Pollution by microplastics in aquatic ecosystems is accumulating at an unprecedented scale, emerging as a new surface for biofilm formation and gene exchange. In this study, we determined the permissiveness of aquatic bacteria towards a model antibiotic resistance plasmid, comparing communities that form biofilms on microplastics vs. those that are free-living. We used an exogenous and red-fluorescent E. coli donor strain to introduce the green-fluorescent broad-host-range plasmid pKJK5 which encodes for trimethoprim resistance. We demonstrate an increased frequency of plasmid…

See more and a link to full text

Transferable resistance to cefotaxime, cefoxitin, cefamandole and cefuroxime in clinical isolates of Klebsiella pneumoniae and Serratia marcescens

Author: Knothe, H.; Shah, P.; Krcmery, V.; Antal, M.; Mitsuhashi, S. Description: In conjugational crosses, three Klebsiella pneumoniae strains and one Serratia marcescens strain have been demonstrated to transfer resistance determinants to newer types of cephalosporins. While Klebsiella strains donated cefotaxime, cefamandole and cefuroxime resistance to Escherichia coli K-12 recipients, the genetic analysis of exconjugants after the transfer of plasmids from Serratia strains to Proteus or Salmonella recipients showed that the cefoxitin resistance determinant was also co-transferred. In subsequent transfer cycles of this plasmid, cefotaxime and cefoxitin resistance determinants segregated…

See more and a link to full text

Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: inhibitory activity against bacteria

Author: Sobha, S.; Mahalakshmi, R.; Raman, N. Description: A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped…

See more and a link to full text

Assembly dynamics of the bacterial MinCDE system and spatial regulation of the Z ring

Author: Lutkenhaus, J. Description: The positioning of a cytoskeletal element that dictates the division plane is a fundamental problem in biology. The assembly and positioning of this cytoskeletal element has to be coordinated with DNA segregation and cell growth to ensure that equal-sized progeny cells are produced, each with a copy of the chromosome. In most prokaryotes, cytokinesis involves positioning a Z ring assembled from FtsZ, the ancestral homologue of tubulin. The position of the Z ring is determined by a gradient of negative regulators of Z-ring assembly. In Escherichia…

See more and a link to full text

FtsK is an essential cell division protein that is localized to the septum and induced as part of the SOS response

Author: Wang, L.; Lutkenhaus, J. Description: The role of ftsK in the growth of Escherichia coli was examined by turning off its expression. This resulted in smooth filaments without constrictions, indicating that FtsK was required at an early step in septation. Consistent with this, FtsK was found to localize to the septum in 70% of the cells, indicating that it was recruited relatively early in this process. FtsK localization required the function of FtsZ and FtsA but not FtsI and FtsQ. Consistent with this, Z rings were present in FtsK-depleted…

See more and a link to full text

Molecular call and response: the physiology of bacterial small RNAs

Author: Richards, G.R.; Vanderpool, C.K. Description: The vital role of bacterial small RNAs (sRNAs) in cellular regulation is now well-established. Although many diverse mechanisms by which sRNAs bring about changes in gene expression have been thoroughly described, comparatively less is known about their biological roles and effects on cell physiology. Nevertheless, for some sRNAs, insight has been gained into the intricate regulatory interplay that is required to sense external environmental and internal metabolic cues and turn them into physiological outcomes. Here, we review examples of regulation by selected sRNAs, emphasizing…

See more and a link to full text