The DNA-recognition fold of Sso7c4 suggests a new member of SpoVT-AbrB superfamily from archaea

Organisms growing at elevated temperatures face the challenge of maintaining the integrity of their genetic materials. Archaea possess unique chromatin proteins for gene organization and information processing. We present the solution structure of Sso7c4 from Sulfolobus solfataricus, which has a homodimeric DNA-binding fold forming a swapped β-loop-β ‘Tai-Chi’ topology. The fold is reminiscent of the N-terminal DNA-binding domain of AbrB and MazE. In addition, several amide resonances in the heteronuclear single quantum coherence spectra of Sso7c4 are shifted and broadened with the addition of small amounts of duplex DNA oligomers. The locations of the corresponding amides in the Sso7c4 structure define its DNA-interacting surface. NMR spectra of DNA titrated with the protein further indicated that Sso7c4 interacts with DNA in the major groove. Taken together, a plausible model for the Sso7c4–DNA complex is presented, in which the DNA double helix is curved around the protein dimer

Pest categorisation of Pantoea stewartii subsp. stewartii

Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Pantoea stewartii subsp. stewartii (hereafter P. s. subsp. stewartii). P. s. subsp. stewartii is a Gram-negative bacterium that causes Stewart’s vascular wilt and leaf blight of sweet corn and maize, a disease responsible for serious crop losses throughout the world. The bacterium is endemic to the USA and is now present in Africa, North, Central and South America, Asia and Ukraine. In the EU, it is reported from Italy with a restricted distribution and under eradication. The bacterium is regulated according to Council Directive 2000/29/EC (Annex IIAI) as a harmful organism whose introduction and spread in the EU is banned on seeds of Zea mays. Other reported potential host plants include various species of the family Poaceae, including weeds, rice (Oryza sativa), oat (Avena sativa) and common wheat (Triticum aestivum), as well as jackfruit (Artocarpus heterophyllus), the ornamental Dracaena sanderiana and the palm Bactris gasipaes, but there is uncertainty about whether these are hosts of P. s. subsp. stewartii or of the other subspecies. The pest could enter the EU via host plants for planting (including seed) and via insect vectors from neighbouring countries. Host plants are widely distributed and climatic conditions are conducive in the EU. P. s. subsp. stewartii could spread by movement of host plants for planting (including seeds) and insect vectors. Impacts could occur on maize and rice. Methods to certify pest freedom of maize seeds are available. The main knowledge gaps concern the availability of vectors in the EU, the level of susceptibility of the maize cultivars grown in the EU, the virulence of strains in recent outbreaks, and the host range of the bacterium. The criteria assessed by the Panel for consideration as a potential quarantine pest are met

A mathematical model of quorum sensing regulated EPS production in biofilm communities

<p>Abstract</p> <p>Background</p> <p>Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities.</p> <p>Model</p> <p>We mathematically model quorum sensing and EPS production in a growing biofilm under various environmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how a biofilm is affected by quorum sensing-regulated EPS production. We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells.</p> <p>Results</p> <p>We find that biofilms that use quorum sensing to induce increased EPS production do not obtain the high cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPS producers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonization mode (with an optimized growth rate), to a protection mode.</p> <p>Conclusions</p> <p>A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have the objective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass as a means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species.</p

Plasmid Structure and Function in Plant-Pathogenic Pseudomonas Syringae (outer-Membrane Proteins)

145 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.Thirty isolates of Pseudomonas syringae pv/ tabaci, pv. angulata, (pathogens on tobacco) pv. coronafaciens, and pv. striafaciens (pathogens on oat) were examined for plasmid DNAs. The strains were obtained from plants throughout the world and some over 30 years ago. Sixteen of the twenty-two tobacco pathogens contain predominately one type of plasmid species, pJP27.00-type. The remaining six tobacco-specific strains do not harbor plasmids. The oat pathogens contain either one, two or three plasmids. DNA homology studies indicate, that the plasmid DNAs are highly conserved. More importantly, the plasmids harbored by strains isolated from one host plant are most stringently conserved. In fact, the plasmids from the tobacco pathogens are, with one exception, indistinguishable by restriction endonuclease digestions and Southern hybridization. There is also extensive homology among plasmids indigenous to the oat-specific Pseudomonas syringae pv. coronafiens and pv. striafaciens strains. However, some of the multiple plasmids within an individual strain are unrelated.Outer membranes of plant-pathogenic Pseudomonas syringae pv. tabaci strains were examined for protein composition based upon plasmid (pBPW1) presence and absence. Sodium dodecyl sulfate polyacrylamide gel electrophoretic resolution of solubilized outer membranes purified on sucrose density gradients identifies an approximately 33,000 dalton protein that is present in cells harboring pBPW1 plasmid. In vitro plasmid DNA-directed transcription and translation experiments establish that the structural gene for this 33,000 dalton protein is located on the pBPW1 plasmid. The expression of this 33,000 dalton protein is eliminated by a Tn3 insertion into the PstI fragment of pBPW1. The third, fourth, and fifth PstI fragment of pBPW1 have been ligated into pWS6 vector plasmid. None of the chimeric plasmids express this 33,000 dalton protein in the Pseudomonas syringae pv. tabaci strain that was transformed separately with the chimeric plasmids. However, the fusion plasmid containing the fourth PstI fragment produces a smaller, approximately 24,000 dalton outer membrane protein. In vitro plasmid DNA-directed transcription translations suggest that this is a second outer membrane protein that is not detectable by the sodium dodecyl sulfate polyacrylamide gel electrophoretic resolution of purified membranes.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

A negative regulator mediates quorum-sensing control of exopolysaccharide production in Pantoea stewartii subsp. stewartii

Classical quorum-sensing (autoinduction) regulation, as exemplified by the lux system of Vibrio fischeri, requires N-acyl homoserine lactone (AHL) signals to stimulate cognate transcriptional activators for the cell density-dependent expression of specific target gene systems. For Pantoea stewartii subsp. stewartii, a bacterial pathogen of sweet corn and maize, the extracellular polysaccharide (EPS) stewartan is a major virulence factor, and its production is controlled by quorum sensing in a population density-dependent manner. Two genes, esaI and esaR, encode essential regulatory proteins for quorum sensing. EsaI is the AHL signal synthase, and EsaR is the cognate gene regulator. esaI, ΔesaR, and ΔesaI-esaR mutations were constructed to establish the regulatory role of EsaR. We report here that strains containing an esaR mutation produce high levels of EPS independently of cell density and in the absence of the AHL signal. Our data indicate that quorum-sensing regulation in P. s. subsp. stewartii, in contrast to most other described systems, uses EsaR to repress EPS synthesis at low cell density, and that derepression requires micromolar amounts of AHL. In addition, derepressed esaR strains, which synthesize EPS constitutively at low cell densities, were significantly less virulent than the wild-type parent. This finding suggests that quorum sensing in P. s. subsp. stewartii may be a mechanism to delay the expression of EPS during the early stages of infection so that it does not interfere with other mechanisms of pathogenesis