Showing papers in "Fems Microbiology Letters in 1999"
TL;DR: 'BLAST 2 Sequences', a new BLAST-based tool for aligning two protein or nucleotide sequences, is described, utilizing the BLAST algorithm for pairwise DNA-DNA or protein-protein sequence comparison.
Abstract: 'BLAST 2 Sequences', a new BLAST-based tool for aligning two protein or nucleotide sequences, is described. While the standard BLAST program is widely used to search for homologous sequences in nucleotide and protein databases, one often needs to compare only two sequences that are already known to be homologous, coming from related species or, e.g. different isolates of the same virus. In such cases searching the entire database would be unnecessarily time-consuming. 'BLAST 2 Sequences' utilizes the BLAST algorithm for pairwise DNA-DNA or protein-protein sequence comparison. A World Wide Web version of the program can be used interactively at the NCBI WWW site (http://www.ncbi.nlm.nih.gov/gorf/bl2.++ +html). The resulting alignments are presented in both graphical and text form. The variants of the program for PC (Windows), Mac and several UNIX-based platforms can be downloaded from the NCBI FTP site (ftp://ncbi.nlm.nih.gov).
2,244 citations
TL;DR: The results indicated that the criterion for isolation of phosphate solubilizers based on the formation of visible halo/zone on agar plates is not a reliable technique, and soil microbes should be screened in NBRIP broth assay for the identification of the most efficient phosphate soluble inorganic phosphates in liquid medium.
Abstract: A novel defined microbiological growth medium, National Botanical Research Institute's phosphate growth medium (NBRIP), which is more efficient than Pikovskaya medium (PVK), was developed for screening phosphate solubilizing microorganisms. In plate assay the efficiency of NBRIP was comparable to PVK; however, in broth assay NBRIP consistently demonstrated about 3-fold higher efficiency compared to PVK. The results indicated that the criterion for isolation of phosphate solubilizers based on the formation of visible halo/zone on agar plates is not a reliable technique, as many isolates which did not show any clear zone on agar plates solubilized insoluble inorganic phosphates in liquid medium. It may be concluded that soil microbes should be screened in NBRIP broth assay for the identification of the most efficient phosphate solubilizers.
1,834 citations
TL;DR: In this article, the authors describe several systems utilizing Gram-positive biocontrol agents that have been researched in depth and provide models for the future of biOControl.
Abstract: Biological control offers an environmentally friendly alternative to the use of pesticides for controlling plant diseases. Unfortunately, growers continue to use chemical control over biological agents, and lack of knowledge often contributes to the downfall of a biocontrol agent. Knowledge of the biological environment in which the agent will be used and of how to produce a stable formulation are both critical to successful biocontrol. Certain Gram-positive bacteria have a natural formulation advantage over their Gram-negative counterparts: the spore. Although the Gram-positive bacteria have not been as well represented in the biocontrol literature, their spore-forming abilities and historical industrial uses bode well for biocontrol success. Here we describe several systems utilizing Gram-positive biocontrol agents that have been researched in depth and provide models for the future of biocontrol.
645 citations
TL;DR: Significant sequence similarities are demonstrated between these regions in numerous histidine kinases, methyl-accepting proteins, adenylyl cyclases and other prokaryotic signalling proteins that possess roles of regulating the phosphorylation or methylation of homodimeric receptors.
Abstract: Mutations in the cytoplasmic linker regions of receptor histidine kinase and chemoreceptor proteins have been shown previously to significantly impair receptor functions. Here we demonstrate significant sequence similarities between these regions in numerous histidine kinases, methyl-accepting proteins, adenylyl cyclases and other prokaryotic signalling proteins. It is suggested that these ‘HAMP domains’ possess roles of regulating the phosphorylation or methylation of homodimeric receptors by transmitting the conformational changes in periplasmic ligand-binding domains to cytoplasmic signalling kinase and methyl-acceptor domains.
411 citations
TL;DR: FramePlot is a web-based tool for predicting protein-coding regions in bacterial DNA with a high G + C content, such as Streptomyces, which provides for easy distinction of protein- coding regions from non-c coding regions.
Abstract: FramePlot is a web-based tool for predicting protein-coding regions in bacterial DNA with a high G+C content, such as Streptomyces. The graphical output provides for easy distinction of protein-coding regions from non-coding regions. The plot is a clickable map. Clicking on an ORF provides not only the nucleotide sequence but also its deduced amino acid sequence. These sequences can then be compared to the NCBI sequence database over the Internet. The program is freely available for academic purposes at http://www.nih.go.jp/~jun/cgi-bin/frameplot.pl.
389 citations
TL;DR: PCR-ribotying, a typing method based on polymorphism in the 16S-23S intergenic spacer region, has been recently used to investigate outbreaks due to Clostridium difficile, but this method generates bands of high and close molecular masses which are difficult to separate on agarose gel electrophoresis.
Abstract: PCR-ribotyping, a typing method based on polymorphism in the 16S-23S intergenic spacer region, has been recently used to investigate outbreaks due to Clostridium difficile. However, this method generates bands of high and close molecular masses which are difficult to separate on agarose gel electrophoresis. To improve reading of banding patterns of PCR-ribotyping applied to C. difficile, a partial sequencing of the rRNA genes (16S and 23S) and intergenic spacer region has been performed, then a new set of primers located closer to the intergenic spacer region has been defined. The new PCR gave reproducible patterns of bands easy to separate on agarose gel electrophoresis. Each of the 10 serogroups and 11 subgroups of serogroup A produced a different pattern. This typing method has evidenced major qualities such as easiness, rapidity and reproducibility. However, its discriminatory power has to be evaluated to validate its importance as a typing tool for C. difficile.
379 citations
TL;DR: An exponential linear destruction was observed for Escherichia coli O157:H7 and Salmonella typhimurium in cattle manure and manure slurry stored at 4, 20 or 37 degrees C and the observed order of destruction makes it possible to predict storage conditions that will lead to a predetermined level of reduction of the two pathogens.
Abstract: An exponential linear destruction was observed for Escherichia coli O157:H7 and Salmonella typhimurium in cattle manure and manure slurry stored at 4, 20 or 37°C. The resulting decimal reduction times ranged from 6 days to 3 weeks in manure and from 2 days to 5 weeks in manure slurry. The main effects of time as well as temperature were pronounced with the most rapid destruction at 37°C. The ammonia concentration in manure increased slightly during storage but did not exceed 0.1%. pH values in the deeper layers of manure remained constant except at 37°C when the pH increased by 1 unit in 60 days. In the surface layers of manure, pH increased by 1.5–2 units, the oxidation-reduction potential of the manure declined rapidly to values below −200 mV. These changes do not seem to be reflected in changing rates of bacterial destruction. The observed order of destruction makes it possible to predict storage conditions (temperature and time) that will lead to a predetermined level of reduction of the two pathogens.
320 citations
TL;DR: A thermophilic microorganism, Bacillus thermoleovorans ID-1, isolated from hot springs in Indonesia, showed extracellular lipase activity and high growth rates on lipid substrates at elevated temperatures.
Abstract: A thermophilic microorganism, Bacillus thermoleovorans ID-1, isolated from hot springs in Indonesia, showed extracellular lipase activity and high growth rates on lipid substrates at elevated temperatures. On olive oil (1.5%, w/v) as the sole carbon source, the isolate ID-1 grew very rapidly at 65°C with its specific growth rate (2.50 h−1) and its lipase activity reached the maximum value of 520 U l−1 during the late exponential phase and then decreased. In addition to this, isolate ID-1 could grow on a variety of lipid substrates such as oils (olive oil, soybean oil and mineral oil), triglycerides (triolein, tributyrin) and emulsifiers (Tween 20, 40). The excreted lipase of ID-1 was purified 223-fold to homogeneity by ammonium sulfate precipitation, DEAE-Sephacel ion-exchange chromatography and Sephacryl S-200 gel filtration chromatography. As a result, the relative molecular mass of the lipase was determined to be 34 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme showed optimal activity at 70–75°C and pH 7.5 and exhibited 50% of its original activity after 1 h incubation at 60°C and 30 min at 70°C and its catalytic function was activated in the presence of Ca2+ or Zn2+.
290 citations
TL;DR: The nature of both the wound and primary septicemia infections, the virulence factors known or believed to be involved in these infections, possible immunotherapy, and some thoughts on the possibility that not all strains of this pathogen are virulent are found are described.
Abstract: This review describes the factors which are currently recognized as being central to the virulence of the human pathogen, Vibrio vulnificus. This estuarine/marine bacterium occurs in high numbers in molluscan shellfish, primarily oysters, and its ingestion in raw oysters results in a ca. 60% mortality in those persons who are susceptible to this bacterium. The organism is also able to produce life-threatening wound infections. We describe here the nature of both the wound and primary septicemia infections, the virulence factors known or believed to be involved in these infections, possible immunotherapy, and some thoughts on the possibility that not all strains of this pathogen are virulent.
274 citations
TL;DR: The aim of this review is to highlight the biodegradative capabilities of microalgae on aromatic compounds, ranging from simple monocyclic to more complex polycyclic pollutants.
Abstract: The microbial degradation of aromatic pollutants has been well characterized over a period of more than 30 years. The microbes of most interest have been bacteria and fungi. Only relatively recently has the question of how algae figure in the catabolism of these compounds attracted a degree of interest. The aim of this review is to highlight the biodegradative capabilities of microalgae on aromatic compounds, ranging from simple monocyclic to more complex polycyclic pollutants. This paper will briefly encompass studies which have investigated the growth on and the oxidation of these compounds by algae, as well as a more detailed characterization of the catabolic sequences involved in the transformation of these compounds.
263 citations
TL;DR: The idea is now emerging that this type of yeast enzyme could offer an alternative to fungal enzymes for industrial applications.
Abstract: When grown in the appropriate medium, several yeast species produce pectinases able to degrade pectic substances. It is mainly exocellular endopolygalacturonases that break pectins or pectate down by hydrolysis of α-1,4-glycosidic linkages in a random way. Biochemical characterisation of these enzymes has shown that they have an optimal pH in the acidic region and an optimal temperature between 40 and 55°C. Their production by yeasts is a constitutive feature and is repressed by the glucose concentration and aeration. Pectic substances and their hydrolysis products are used as carbon sources by a limited number of yeasts and hence these enzymes must be involved in the colonisation of different parts of plants, including fruits. The first yeast pectic enzyme (encoded by the PSE3 gene) was cloned from Tichosporon penicillatum. Recently, a polygalacturonase-encoding gene from Saccharomyces cerevisiae has been cloned and overexpressed in several strains and the gene for an extracellualar endopolygalacturonase from Kluyveromyces marxianus has also been described. Taking all the results together, the idea is now emerging that this type of yeast enzyme could offer an alternative to fungal enzymes for industrial applications.
TL;DR: A new model for the dimerisation of the nucleotide-binding domains that embraces the notion that the C motif from one subunit forms part of the ATP-binding site in the opposite subunit is argued and incorporated into the recently reported beta-barrel model for P-glycoprotein.
Abstract: The ABC superfamily is a diverse group of integral membrane proteins involved in the ATP-dependent transport of solutes across biological membranes in both prokaryotes and eukaryotes. Although ABC transporters have been studied for over 30 years, very little is known about the mechanism by which the energy of ATP hydrolysis is used to transport substrate across the membrane. The recent report of the high resolution crystal structure of HisP, the nucleotide-binding subunit of the histidine permease complex of Salmonella typhimurium, represents a significant breakthrough toward the elucidation of the mechanism of solute translocation by ABC transporters. In this review, we use data from the crystallographic structures of HisP and other nucleotide-binding proteins, combined with sequence analysis of a subset of atypical ABC transporters, to argue a new model for the dimerisation of the nucleotide-binding domains that embraces the notion that the C motif from one subunit forms part of the ATP-binding site in the opposite subunit. We incorporate this dimerisation of the ATP-binding domains into our recently reported β-barrel model for P-glycoprotein and present a general model for the cooperative interaction of the two nucleotide-binding domains and the translocation of mechanical energy to the transmembrane domains in ABC transporters.
TL;DR: Derived maximum likelihood and DNA distance trees indicated that Microcystis can be divided into three clusters, andPhylogenetic analysis based on intergenic spacer sequences was thought to be effective for understanding relationships among closely related species and strains.
Abstract: 16S to 23S ribosomal DNA internal transcribed spacer sequences of 47 strains of the genus Microcystis were determined. Derived maximum likelihood and DNA distance trees indicated that Microcystis can be divided into three clusters. The first cluster included toxic and non-toxic strains, the second only toxic ones, and the third only non-toxic ones. The tree topologies were not necessarily correlated with morphospecies distinction or phycobilin pigment composition, and one genotype may have more than one morphotype. Phylogenetic analysis based on intergenic spacer sequences was thought to be effective for understanding relationships among closely related species and strains.
TL;DR: Variations in the presence of the different genes when comparing staphylococcal isolates of human and animal origin were observed and specific primers to detect some of these classes designed.
Abstract: A classification of the different erm gene classes based on published sequences was performed, and specific primers to detect some of these classes designed. The presence of ermA (Tn554), ermB (class IV) and ermC (class VI) was determined by PCR in a total of 113 enterococcal, 77 streptococcal and 68 staphylococcal erythromycin resistant isolates of animal and human origin. At least one of these genes was detected in 88% of the isolates. Four isolates contained more than one erm gene. ermB dominated among the enterococci (88%) and streptococci (90%) and ermC among staphylococci (75%) with ermA (Tn554) present in some isolates (16%). Variations in the presence of the different genes when comparing staphylococcal isolates of human and animal origin were observed.
TL;DR: It is shown that the negative effect of the cpxA mutation on biofilm formation results from a decreased transcription of the curlin encoding csgA gene, and the existence of a new signal transduction pathway involved in the adherence process in addition to the EnvZ-OmpR two-component system is proposed.
Abstract: In a genetic screening directed to identify genes involved in biofilm formation, mutations in the cpxA gene were found to reduce biofilm formation by affecting microbial adherence to solid surfaces. This effect was detected in Escherichia coli K12 as well as in E. coli strains isolated from patients with catheter-related bacteremia. We show that the negative effect of the cpxA mutation on biofilm formation results from a decreased transcription of the curlin encoding csgA gene. The effect of the cpxA mutation could not be observed in cpxR− mutants, suggesting that they affect the same regulatory pathway. The cpxA101 mutation abolishes cpxA phosphatase activity and results in the accumulation of phosphorylated CpxR. Features of the strain carrying the cpxA101 mutation are a reduced ability to form biofilm and low levels of csgA transcription. Our results indicate that the cpxA gene increases the levels of csgA transcription by dephosphorylation of CpxR, which acts as a negative regulator at csgA. Thus, we propose the existence of a new signal transduction pathway involved in the adherence process in addition to the EnvZ-OmpR two-component system.
TL;DR: The non-haemolytic enterotoxin from Bacillus cereus has been sequenced and Transcription of the operon seems to be positively regulated by plcR, a gene that also regulates phospholipase C expression.
Abstract: The non-haemolytic enterotoxin from Bacillus cereus has been sequenced. It is composed of three components, non-haemolytic enterotoxin A, B and C of 41.0, 39.8 and 36.5 kDa, respectively. Transcription of the operon seems to be positively regulated by plcR, a gene that also regulates phospholipase C expression. There is substantial similarity between the three proteins of non-haemolytic enterotoxin and between the non-haemolytic enterotoxin and haemolytic enterotoxin proteins.
TL;DR: Using laboratory microcosms, it is shown that Escherichia coli O157 survives and replicates in a common environmental protozoan, Acanthamoeba polyphaga, which may constitute an important environmental reservoir for transmission of E. coli O 157 and other pathogens.
Abstract: Intra-protozoal growth of bacterial pathogens has been associated with increased environmental survival, virulence and resistance to biocides and antibiotics. Using laboratory microcosms we have shown that Escherichia coli 0157 survives and replicates in a common environmental protozoan, Acanthamoeba polyphaga. As protozoa are widely distributed in soils and effluents, they may constitute an important environmental reservoir for transmission of E. coli 0157 and other pathogens.
TL;DR: Degenerated oligonucleotide primers were designed to amplify fragments of ketosynthase genes from polyketide antibiotics producing Streptomyces spp.
Abstract: Degenerated oligonucleotide primers were designed to amplify fragments of ketosynthase genes from polyketide antibiotics producing Streptomyces spp. and bacterial strains enriched from soil samples. Cell lysates were used as templates in amplification, so time-consuming DNA purification was avoided. A phylogenetic tree constructed from the amino acid sequences of the amplified fragments shows a distribution of spore pigments and antibiotics in separate classes. In addition, several different subgroups form within the antibiotics group. Anthracyclines were divided into separate branches according to the starter unit used in biosynthesis.
TL;DR: A fragment of a S. aureus genomic library, screened with a probe adjacent to the transposon insertion of a sae::Tn551 mutant, was cloned into a bifunctional vector and revealed the presence of two genes, designated saeR and saeS, encoding a response regulator and a histidine protein kinase, respectively, with high homology to other bacterial two-component regulatory systems.
Abstract: sae is a regulatory locus that activates the production of several exoproteins in Staphylococcus aureus. A 3.4-kb fragment of a S. aureus genomic library, screened with a probe adjacent to the transposon insertion of a sae::Tn551 mutant, was cloned into a bifunctional vector. This fragment was shown to carry the sae locus by restoration of exoprotein production in sae mutants. The sae locus was mapped to the SmaI-D fragment of the staphylococcal chromosome by pulse-field electrophoresis. Sequence analysis of the cloned fragment revealed the presence of two genes, designated saeR and saeS, encoding a response regulator and a histidine protein kinase, respectively, with high homology to other bacterial two-component regulatory systems.
TL;DR: A glucose dehydrogenase that is induced 5-fold by phosphate starvation, has been characterized from a bacterium isolated from alkaline Indian vertisol soils indicating that GDH activity is required to solubilize phosphate.
Abstract: A glucose dehydrogenase (GDH) that is induced 5-fold by phosphate starvation, has been characterized from a bacterium isolated from alkaline Indian vertisol soils. The bacterium was identified as Enterobacter asburiae based on 16S rRNA analysis. Concomitant with GDH induction, glucose was oxidized and secreted as gluconate (50 mM). Excretion of this acid caused a reduction in soil pH and the release of phosphate and iron. Mutants deficient in GDH activity failed to release phosphate from alkaline soils indicating that GDH activity is required to solubilize phosphate.
TL;DR: Recent advances in the knowledge of interactions of Tol-Pal proteins with other envelope components, or with group A colicins, are presented, together with current hypotheses about the role of the Tol proteins in outer membrane stability.
Abstract: The Tol proteins of Escherichia coli are involved in outer membrane stability. They are also required for the uptake of the group A colicins and the translocation of filamentous phage DNA into the cytoplasm. The tol-pal genes constitute two operons in the E. coli genome, orf1tolQRA and tolBpalorf2. The TolQ TolR TolA proteins form a complex in the cytoplasmic membrane, while TolB and Pal interact near the outer membrane. Most of the amino acid residues of TolA, TolB, TolR and Pal are localized in the periplasm. Recent advances in the knowledge of interactions of Tol-Pal proteins with other envelope components, or with group A colicins, are presented, together with current hypotheses about the role of the Tol proteins in outer membrane stability.
TL;DR: The toxicity of four of the most agriculturally important mycotoxins (the trichothecenes, and the polyketide-derived mycotoxin; aflatoxins, fumonisins and sterigmatocystin) are discussed and their chemical structure described.
Abstract: Mycotoxins are secondary metabolites produced by many important phytopathogenic and food spoilage fungi including Aspergillus, Fusarium and Penicillium species. The toxicity of four of the most agriculturally important mycotoxins (the trichothecenes, and the polyketide-derived mycotoxins; aflatoxins, fumonisins and sterigmatocystin) are discussed and their chemical structure described. The steps involved in the biosynthesis of aflatoxin and sterigmatocystin and the experimental techniques used in the cloning and molecular characterisation of the genes involved in the pathway are described in detail. The biosynthetic genes involved in the fumonisin and trichothecene biosynthetic pathways are also outlined. The potential benefits gained from an increased knowledge of the molecular organisation of these pathways together with the mechanisms involved in their regulation are also discussed.
TL;DR: Cotransduction tests demonstrate that the resistance genes, although not organized in a unique integron, are tightly clustered on the Salmonella chromosome.
Abstract: Epidemic strain Salmonella typhimurium DT104 is characterized by various multiresistance patterns. At least some of the resistance genes are organized as integrons. Resistance genes of DT104 isolates can be efficiently transduced by P22-like phage ES18 and by phage PDT17 which is released by all DT104 isolates so far analyzed. Cotransduction tests demonstrate that the resistance genes, although not organized in a unique integron, are tightly clustered on the Salmonella chromosome. The spread of resistance genes in this strain by generalized transduction is discussed.
TL;DR: These data represent the first report, to the authors' knowledge, of intergeneric transfer of a conjugative transposon in a mixed species biofilm and demonstrates the ability of conjugatives transposons to disseminate antibiotic resistance genes in a Mixed species environment.
Abstract: A tetracycline resistance profile was established from a microcosm dental plaque in a constant depth film fermenter. The fermenter was inoculated with a Bacillus subtilis strain which contained the conjugative transposon, Tn5397, which confers tetracycline resistance upon its host. After 6 hour and 24 hour the tetracycline resistance profile of the biofilm was redetermined and a tetracycline resistant Streptococcus species was isolated. A molecular analysis of this strain confirmed that Tn5397 was present in the genomic DNA of the isolate. These data represent the first report, to our knowledge, of intergeneric transfer of a conjugative transposon in a mixed species biofilm and demonstrates the ability of conjugative transposons to disseminate antibiotic resistance genes in a mixed species environment.
TL;DR: A new chloramphenicol resistance gene from Salmonella typhimurium DT104, designated floR, also conferring resistance to florfenicol, was characterized and suggested that it belongs to the 12-TMS (transmembrane segments) multidrug efflux pumps family.
Abstract: A new chloramphenicol resistance gene from Salmonella typhimurium DT104, designated floR, also conferring resistance to florfenicol, was characterized. Sequence analysis of the deduced FloR protein suggested that it belongs to the 12-TMS (transmembrane segments) multidrug efflux pumps family. The floR gene, and the downstream sequenced tetR and tetA tetracycline resistance genes, were surrounded by two class 1 integrons. The first one contained the resistance gene aadA2 and a deleted sulI resistance gene. The second one contained the β-lactamase gene pse1 and a complete sulI gene. Thus, the floR gene is included in a multiresistance locus of at least 12.5 kb. Its particular organization and chromosomal location could be involved in the antibioresistance pattern stability of the DT104 Salmonella typhimurium strains.
TL;DR: From a cosmid library of Streptomyces cyanogenus S136, DNA fragments encompassing approximately 35 kb of the presumed landomycin biosynthetic gene cluster were identified and sequenced, revealing 32 open reading frames most of which could be assigned through data base comparison.
Abstract: From a cosmid library of Streptomyces cyanogenus S136, DNA fragments encompassing approximately 35 kb of the presumed landomycin biosynthetic gene cluster were identified and sequenced, revealing 32 open reading frames most of which could be assigned through data base comparison.
TL;DR: Wolbachia pipientis are intracellular, transovarially inherited alpha-Proteobacteria in invertebrates and F. candida's group E Wolbachia rekindle the question about invasive capacities of free-living ancestral wolbachiae and horizontal transfer.
Abstract: Wolbachia pipientis are intracellular, transovarially inherited α-Proteobacteria in invertebrates. Four major Wolbachia groups exist: A, B (contained in divergent arthropods), C and D (harbored by Nematoda). By means of transmission electron microscopy, we observed Wolbachia-like bacteria in a primitive insect, Folsomia candida (Hexapoda, Collembola, Isotomidae). 16S rDNA analysis proved them to constitute a novel lineage, henceforth named group E, in the wolbachial phylogenetic tree. It shares 97.8% 16S rDNA homology with its nearest neighbors, groups A and B, which diverged from it more recently. We propose (i) a new taxon E for the Wolbachia strain in F. candida, (ii) that the single-described Wolbachia pipientis fall apart into at least three species: C, D and the large E-A-B complex. F. candida's group E Wolbachia rekindle the question about invasive capacities of free-living ancestral wolbachiae and horizontal transfer.
TL;DR: Results show that the AlgC protein plays a central role in the production of the three P. aeruginosa virulence-associated saccharides: alginate, LPS and rhamnolipid.
Abstract: Pseudomonas aeruginosa produces exoproducts correlated with its pathogenicity. One of these virulence-associated traits is the surfactant rhamnolipid. The production of alginate and lipopolysaccharide (LPS) are also of importance for P. aeruginosa virulence. The product of the algC gene (which is involved in alginate production through its phosphomannomutase activity and in LPS synthesis through its phosphoglucomutase activity) participates in rhamnolipid production, presumably catalyzing the first step in the deoxy-thymidine-diphospho-L-rhamnose (dTDP-L-rhamnose) pathway, the conversion of glucose-6-phosphate to glucose-1-phosphate. Other structural alg genes, encoded in the alg operon, are not involved in rhamnolipid nor LPS production. These results show that the AlgC protein plays a central role in the production of the three P. aeruginosa virulence-associated saccharides: alginate, LPS and rhamnolipid.
TL;DR: A survey was performed to gauge the distribution of hlyA and aerA genes in clinical and environmental Aeromonas isolates to find the best prediction of virulence in an animal model.
Abstract: Previous studies have shown that two hemolytic toxins, HlyA and AerA, contribute to the virulence of Aeromonas hydrophila. A survey was performed to gauge the distribution of hlyA and aerA genes in clinical and environmental Aeromonas isolates. For A. hydrophila, A. veronii biotype sobria and A caviae, 96%, 12% and 35% of strains, respectively, were hlyA positive, whereas, 78%, 97%, 41%, respectively, were aerA positive. All virulent A. hydrophila isolates were hlyA+aerA+. This genotype was most common in A. hydrophila (75.4%) followed by A. caviae (29.4%) and A. veronii biotype sobria (9.6%). For A. hydrophila, a two-hemolytic toxin model of virulence provides the best prediction of virulence in an animal model.
TL;DR: It is concluded that the primary staphylococcal target for totarol is the respiratory chain, but that potentiation of methicillin by diterpenes is by interference with PBP 2a expression.
Abstract: Totarol is a diterpene compound extracted from the totara tree. Totarol and eight other diterpenes were found to potentiate methicillin, one reducing the minimum inhibitory concentration of methicillin against resistant Staphylococcus aureus 256-fold. Totarol did not inhibit the synthesis of DNA or peptidoglycan in S. aureus, but reduced the respiration rate by 70%. Under potentiation conditions, diterpenes had only a slight effect on the respiration rate, but had a significant effect on expression of PBP 2a. We conclude that the primary staphylococcal target for totarol is the respiratory chain, but that potentiation of methicillin by diterpenes is by interference with PBP 2a expression.