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PubMed2005

Intra- and interspecific comparisons of bacterial diversity and community structure support coevolution of gut microbiota and termite host.

We investigated the bacterial gut microbiota from 32 colonies of wood-feeding termites, comprising four Microcerotermes species (Termitidae) and four Reticulitermes species (Rhinotermitidae), using terminal restriction fragment length polymorphism analysis and clonal analysis of 16S rRNA. The obtained molecular community profiles were compared statistically between individuals, colonies, locations, and species of termites. Both analyses revealed that the bacterial community structure was remarkably similar within each termite genus, with small but significant differences between sampling sites and/or termite species. In contrast, considerable differences were found between the two termite genera. Only one bacterial phylotype (defined with 97% sequence identity) was shared between the two termite genera, while 18% and 50% of the phylotypes were shared between two congeneric species in the genera Microcerotermes and Reticulitermes, respectively. Nevertheless, a phylogenetic analysis of 228 phylotypes from Microcerotermes spp. and 367 phylotypes from Reticulitermes spp. with other termite gut clones available in public databases demonstrated the monophyly of many phylotypes from distantly related termites. The monophyletic "termite clusters" comprised of phylotypes from more than one termite species were distributed among 15 bacterial phyla, including the novel candidate phyla TG2 and TG3. These termite clusters accounted for 95% of the 960 clones analyzed in this study. Moreover, the clusters in 12 phyla comprised phylotypes from more than one termite (sub)family, accounting for 75% of the analyzed clones. Our results suggest that the majority of gut bacteria are not allochthonous but are specific symbionts that have coevolved with termites and that their community structure is basically consistent within a genus of termites.

Animals↗
PubMedDate not supplied

Study of adjuvant and mitogenic activities of bacterial peptidoglycans with different structures.

The adjuvant and mitogenic properties of bacterial peptidoglycans (PG) of different structures have been compared. The PG from Bacillus megaterium and Staphylococcus aureus were adjuvant-active in the guinea-pig, and mitogenic for guinea-pig and mouse lymphocytes. On the other hand the PG from Micrococcus lysodeikticus and Corynebacterium poinsettiae exerted neither adjuvant nor mitogenic activities. Mitogenic PG were selective B mitogens. They were mitogenic for splenocytes from Nude mice and inactive towards T-cell-enriched populations. They were mitogenic in both germ-free mice and in the C3H/HeJ strain which is unresponsive to lipopolysaccharide.

Adjuvants, Immunologic↗
PubMed2000

Crystal structure of the bacterial conjugation repressor finO.

The conjugative transfer of F-like plasmids is repressed by FinO, an RNA binding protein. FinO interacts with the F-plasmid encoded traJ mRNA and its antisense RNA, FinP, stabilizing FinP against endonucleolytic degradation and facilitating sense-antisense RNA recognition. Here we present the 2.0 A resolution X-ray crystal structure of FinO, lacking its flexible N-terminal extension. FinO adopts a novel, elongated, largely helical conformation. An N-terminal region, previously shown to contact RNA, forms a positively charged alpha-helix (helix 1) that protrudes 45 A from the central core of FinO. A C-terminal region of FinO that is implicated in RNA interactions also extends out from the central body of the protein, adopting a helical conformation and packing against the base of the N-terminal helix. A highly positively charged patch on the surface of the FinO core may present another RNA binding surface. The results of an in vitro RNA duplexing assay demonstrate that the flexible N-terminal region of FinO plays a key role in FinP-traJ RNA recognition, and supports our proposal that this region and the N-terminus of helix 1 interact with and stabilize paired, complementary RNA loops in a kissing complex.

Amino Acid Sequence↗
PubMed2002

Structure of the bacterial RNA polymerase promoter specificity sigma subunit.

The sigma subunit is the key regulator of bacterial transcription. Proteolysis of Thermus aquaticus sigma(A), which occurred in situ during crystallization, reveals three domains, sigma(2), sigma(3), and sigma(4), connected by flexible linkers. Crystal structures of each domain were determined, as well as of sigma(4) complexed with -35 element DNA. Exposed surfaces of each domain are important for RNA polymerase binding. Universally conserved residues important for -10 element recognition and melting lie on one face of sigma(2), while residues important for extended -10 recognition lie on sigma(3). Genetic studies correctly predicted that a helix-turn-helix motif in sigma(4) recognizes the -35 element but not the details of the protein-DNA interactions. Positive control mutants in sigma(4) cluster in two regions, positioned to interact with activators bound just upstream or downstream of the -35 element.

Bacterial Proteins↗
PubMed1988

Structure of a bacterial sensory receptor. A site-directed sulfhydryl study.

Cysteines are substituted at six positions in the aspartate receptor, and these mutant proteins are used to investigate three major facets of receptor structure. 1) The surface of the receptor is examined through measurement of the rate constants for chemical modification of the cysteines by aqueous reagents. Different positions exhibit a range of accessibility (for example, Cys-128 most exposed, Cys-36 most buried). 2) The transmembrane structure of the receptor is determined by reaction of the cysteines with a membrane-impermeant reagent. 3) The spatial proximities in the folded structure of specific pairs of cysteines are investigated by disulfide bond formation. These studies illustrate the usefulness of site-directed sulfhydryl chemistry in the analysis of protein structure.

Cell Membrane↗
PubMed1996

[Pillin structural gene and bacterial adhesion to cultured cell of Pseudomonas aeruginosa isolated from clinical materials].

Thirty-three stocks of Pseudomonas aeruginosa which is an important etiologic agent of opportunistic infections were clinically isolated. The pillin structural gene pilA of the stocks were amplified by polymerase chain reaction (PCR) and classified into 3 groups; 2000 bp (16 stocks; 48.5%), 1300 bp (11 stocks; 33.3%), 550 bp (6 stocks; 18.2%). The adhesiveness of the stocks to cultured human lung cancer origin calu-1 was also determined, their adhesion rate per cell were 39.2%, 24.8%, 22.1% in average respectively. Thus clinically most common 2000 pb group is remarkably easier to adhere to calu-1. Serotypes of the strains were examined to reveal the difference of the distribution that F. G. I types were dominant in 2000 pb group, but E types were major in 1300 bp and 550 bp groups. These data suggest that the gene arrangement of pilA influences adhesiveness to cultured cell and antigenicity of bacteria.

Bacterial Adhesion↗
PubMed1994

Doughnut-shaped structure of a bacterial muramidase revealed by X-ray crystallography.

The integrity of the bacterial cell wall depends on the balanced action of several peptidoglycan (murein) synthesizing and degrading enzymes. Penicillin inhibits the enzymes responsible for peptide crosslinks in the peptidoglycan polymer. Enzymes that act solely on the glycosidic bonds are insensitive to this antibiotic, thus offering a target for the design of antibiotics distinct from the beta-lactams. Here we report the X-ray structure of the periplasmic soluble lytic transglycosylase (SLT; M(r) 70,000) from Escherichia coli. This unique bacterial exomuramidase cleaves the beta-1,4-glycosidic bonds of peptidoglycan to produce small 1,6-anhydromuropeptides. The structure of SLT reveals a 'superhelical' ring of alpha-helices with a separate domain on top which resembles the fold of lysozyme. Site-directed mutagenesis and a crystallographic inhibitor-binding study confirmed that the lysozyme-like domain contains the active site of SLT.

Binding Sites↗
PubMed1995

Use of iron anomalous scattering with multiple models and data sets to identify and refine a weak molecular replacement solution: structure analysis of cytochrome c' from two bacterial species.

The structure of cytochrome c' from two bacterial species, Alcaligenes sp and Alcaligenes denitrificans, have been determined from X-ray diffraction data to 3.0 A resolution using the anomalous scattering of the single Fe atom in each to identify and refine a weak molecular-replacement solution. Molecular-replacement studies, with the program AMORE, used two isomorphous data sets (from the two species), two independent search models (the cytochromes c' from Rhodospirillum molischianum and Rhodospirillum rubrum), both with and without side chains, and two different resolution ranges (10.0-4.0 and 15.0-3.5A) to generate a large number of potential solutions. No single solution stood out and none appeared consistently. The Fe-atom position in each structure was then determined from its anomalous-scattering contribution and all molecular- replacement solutions were discarded which did not (i) place the Fe atom correctly and (ii) orient the molecule such that a crystallographic twofold axis generated a dimer like those of the two search models. Finally, electron-density maps phased solely by the Fe-atom anomalous scattering were calculated. As these were combined and subjected to solvent flattening and histogram matching (with the program SQUASH), correlation with the remaining molecular-replacement solutions identified one as correct and enabled it to be improved and subjected to preliminary refinement. The correctness of the solution is confirmed by parallel isomorphous-replacement studies.

Journal Article↗
PubMed2003

Molecular modeling of the three-dimensional structure of the bacterial RNase P holoenzyme.

Bacterial ribonuclease P (RNase P), an enzyme involved in tRNA maturation, consists of a catalytic RNA subunit and a protein cofactor. Comparative phylogenetic analysis and molecular modeling have been employed to derive secondary and tertiary structure models of the RNA subunits from Escherichia coli (type A) and Bacillus subtilis (type B) RNase P. The tertiary structure of the protein subunit of B.subtilis and Staphylococcus aureus RNase P has recently been determined. However, an understanding of the structure of the RNase P holoenzyme (i.e. the ribonucleoprotein complex) is lacking. We have now used an EDTA-Fe-based footprinting approach to generate information about RNA-protein contact sites in E.coli RNase P. The footprinting data, together with results from other biochemical and biophysical studies, have furnished distance constraints, which in turn have enabled us to build three-dimensional models of both type A and B versions of the bacterial RNase P holoenzyme in the absence and presence of its precursor tRNA substrate. These models are consistent with results from previous studies and provide both structural and mechanistic insights into the functioning of this unique catalytic RNP complex.

Amino Acid Sequence↗
PubMed2005

Crystal structure of the bacterial YhcH protein indicates a role in sialic acid catabolism.

The yhcH gene is part of the nan operon in bacteria that encodes proteins involved in sialic acid catabolism. Determination of the crystal structure of YhcH from Haemophilus influenzae was undertaken as part of a structural genomics effort in order to assist with the functional assignment of the protein. The structure was determined at 2.2-A resolution by multiple-wavelength anomalous diffraction. The protein fold is a variation of the double-stranded beta-helix. Two antiparallel beta-sheets form a funnel opened at one side, where a putative active site contains a copper ion coordinated to the side chains of two histidine and two carboxylic acid residues. A comparison to other proteins with a similar fold and analysis of the genomic context suggested that YhcH may be a sugar isomerase involved in processing of exogenous sialic acid.

Amino Acid Sequence↗
PubMed2000

Bacterial phospholipase A: structure and function of an integral membrane phospholipase.

Within the large family of lipolytic enzymes, phospholipases constitute a very diverse subgroup with physiological functions such as digestion and signal transduction. Most phospholipases may associate with membranes at the lipid-water interface. However, in many Gram-negative bacteria, a phospholipase is present which is located integrally in the bacterial outer membrane. This phospholipase (outer membrane phospholipase A or OMPLA) is involved in transport across the bacterial outer membrane and has been implicated in bacterial virulence. OMPLA is calcium dependent and its activity is strictly regulated by reversible dimerisation. Recently the crystal structure of this integral membrane enzyme has been elucidated. In this review, we summarise the implications of these structural data for the understanding of the function and regulation of OMPLA, and discuss a mechanism for phospholipase dependent colicin release in Escherichia coli.

Amino Acid Sequence↗
PubMedDate not supplied

[Studies on the growth and reproduction of bacterial communities on structural materials of the international space station].

Probability of microbial growth and reproduction on the ISS interior and equipment materials varying in chemical composition was studied with the strains of Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus saprophyticus, Pseudomonas putida etc. sampled from the ISS environment. Controls were ground reference strains of same bacterial species. Based on our results, some of the microorganisms are able to survive and proliferate on structural materials; the ability was greater in space isolates as compared with their ground analogs. The greatest ability to grow and proliferate on materials was demonstrated by Bacillus subtilis.

Bacillus subtilis↗
PubMed1997

Solution secondary structure of a bacterially expressed peptide from the receptor binding domain of Pseudomonas aeruginosa pili strain PAK: A heteronuclear multidimensional NMR study.

The C-terminal receptor binding region of Pseudomonas aeruginosa pilin protein strain PAK (residues 128-144) has recently been the target for the design of a synthetic peptide vaccine effective against multiple strains of P. aeruginosa infection. We have successfully cloned and bacterially expressed a 15N-labeled PAK pilin peptide spanning residues 128-144 of the intact PAK pilin protein, PAK 128-144(Hs145), and have determined the solution secondary structure of this peptide using heteronuclear multidimensional NMR spectroscopy. The oxidized recombinant peptide exists as a major (trans) and minor (cis) species in solution, arising from isomerization around the Ile138-Pro139 peptide bond. The pattern of NOEs, temperature coefficients, and coupling constants observed for the trans isomer demonstrate the presence of a type I beta-turn and a type II beta-turn spanning Asp134-Glu-Gln-Phe137 and Pro139-Lys-Gly-Cys142, respectively. This is in agreement with the NMR solution structure of the trans isomer of a synthetic PAK 128-144 peptide which showed a type I and a type II beta-turn in these same regions of the sequence [McInnes, C., Sönnichsen, F. D., Kay, C. M., Hodges, R. S., and Sykes, B. D. (1993) Biochemistry 32, 13432-13440; Campbell, A. P., McInnes, C., Hodges, R. S., and Sykes, B. D. (1995) Biochemistry 34, 16255-16268]. The pattern of NOEs, temperature coefficients, and coupling constants observed for the cis isomer also demonstrate a type II beta-turn spanning Pro139-Lys-Gly-Cys142, but suggest a second beta-turn spanning Asp132-Gln-Asp-Glu135. Thus, the cis isomer may also possess a double-turn motif (like the trans isomer), but with different spacing between the turns and a different placement of the first turn in the sequence. The discovery of a double-turn motif in the trans (and cis) recombinant PAK pilin peptide is an extremely important result since the double turn has been implicated as a structural requirement for the recognition of both receptor and antibody. These results pave the way for future isotope-edited NMR studies of the labeled recombinant PAK pilin peptide bound to antibody and receptor, studies integral to the design of an effective synthetic peptide vaccine.

Amino Acid Sequence↗
PubMed1984

Isolation and structure of the bacterial sex pheromone, cAD1, that induces plasmid transfer in Streptococcus faecalis.

The Streptococcus faecalis sex pheromone cAD1, which is involved in the conjugative transfer of the hemolysin plasmid pAD1, has been isolated and its structure determined. Its Mr is 818 and its amino acid sequence is H-Leu-Phe-Ser-Leu-Val-Leu-Ala-Gly-OH. A replicate of the pheromone synthesized by the liquid-phase method showed the same biological activity and chromatographic behavior as the isolated cAD1. Pheromone activity was detectable at a concentration of approximately 5 X 10(-11) M.

Amino Acid Sequence↗
PubMed1999

Structural deformation of bacterial biofilms caused by short-term fluctuations in fluid shear: an in situ investigation of biofilm rheology.

The physical properties (rheology) of biofilms will determine the shape and mechanical stability of the biofilm structure and consequently affect both mass transfer and detachment processes. Biofilm viscoelasticity is also thought to increase fluid energy losses in pipelines. Yet there is very little information on the rheology of intact biofilms. This is due in part to the difficulty in using conventional testing techniques. The size and nature of biofilms makes them difficult to handle, while removal from a surface destroys the integrity of the sample. We have developed a method which allowed us to conduct simple stress-strain and creep experiments on mixed and pure culture biofilms in situ by observing the structural deformations caused by changes in hydrodynamic shear stress (tau(w)). The biofilms were grown under turbulent pipe flow (flow velocity (u) = 1 m/s, Reynolds number (Re) = 3600, tau(w) = 5. 09 N/m(2)) for between 12 and 23 days. The resulting biofilms were heterogeneous and consisted of filamentous streamers that were readily deformed by changes in tau(w). At tau(w) of 10.11 N/m(2) the streamers were flattened so that the thickness was reduced by 25%. We estimated that the shear modulus (G) of the mixed culture biofilm was 27 N/m(2) and the apparent elastic modulus (E(app)) of both biofilms was in the range of 17 to 40 N/m(2). The biofilms behaved like elastic and viscoelastic solids below the tau(w) at which they were grown but behaved like viscoelastic fluids at elevated tau(w). The implications of these results for fluid energy losses and the processes of mass transfer and detachment are discussed.

Bacteria↗
PubMed1994

Rhizobium meliloti lipooligosaccharide nodulation factors: different structural requirements for bacterial entry into target root hair cells and induction of plant symbiotic developmental responses.

Rhizobium meliloti produces lipochitooligosaccharide nodulation NodRm factors that are required for nodulation of legume hosts. NodRm factors are O-acetylated and N-acylated by specific C16-unsaturated fatty acids. nodL mutants produce non-O-acetylated factors, and nodFE mutants produce factors with modified acyl substituents. Both mutants exhibited a significantly reduced capacity to elicit infection thread (IT) formation in alfalfa. However, once initiated, ITs developed and allowed the formation of nitrogen-fixing nodules. In contrast, double nodF/nodL mutants were unable to penetrate into legume hosts and to form ITs. Nevertheless, these mutants induced widespread cell wall tip growth in trichoblasts and other epidermal cells and were also able to elicit cortical cell activation at a distance. NodRm factor structural requirements are thus clearly more stringent for bacterial entry than for the elicitation of developmental plant responses.

Biological Assay↗