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PubMed2006

Detection and characterization of bacteria from the potato rhizosphere degrading N-acyl-homoserine lactone.

Quorum sensing plays a role in the regulation of soft rot diseases caused by the plant pathogenic bacterium Pectobacterium carotovorum subsp. carotovorum. The signal molecules involved in quorum sensing in P. carotovorum subsp. carotovorum belong to the group of N-acyl homoserine lactones (AHLs). In our study, we screened bacteria isolated from the potato rhizosphere for the ability to degrade AHLs produced by P. carotovorum subsp. carotovorum. Six isolates able to degrade AHLs were selected for further studies. According to 16S rDNA sequence analysis and fatty acid methyl ester profiling, the isolates belonged to the genera Ochrobactrum, Rhodococcus, Pseudomonas, Bacillus, and Delftia. For the genera Ochrobactrum and Delftia, for the first time AHL-degrading isolates were found. Data presented in this study revealed for the first time that Ochrobactrum sp. strain A44 showed the capacity to inactivate various synthetic AHL molecules; the substituted AHLs were inactivated with a lower efficiency than the unsubstituted AHLs. Compared with the other isolates, A44 was very effective in the degradation of AHLs produced by P. carotovorum subsp. carotovorum. It was verified by polymerase chain reaction, DNA-DNA hybridization, and a lactone ring reconstruction assay that Ochrobactrum sp. strain A44 did not possess AHL lactonase activity. AHL degradation in Ochrobactrum sp. strain A44 occurred intracellularly; it was not found in the culture supernatant. AHL-degrading activity of A44 was thermo sensitive. Experiments in planta revealed that Ochrobactrum sp. strain A44 significantly inhibited the maceration of potato tuber tissue. Since A44 did not produce antibiotics, the attenuation of the decay might be due to the quenching of quorum- sensing-regulated production of pectinolytic enzymes. The strain can potentially serve to control P. carotovorum subsp. carotovorum in potato.

4-Butyrolactone↗
PubMed2006

Description of Pseudochrobactrum gen. nov., with the two species Pseudochrobactrum asaccharolyticum sp. nov. and Pseudochrobactrum saccharolyticum sp. nov.

Two Gram-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile bacteria (CCUG 46016(T) and CCUG 33852(T)), isolated from a knee aspirate of a 66-year-old man and an industrial glue, respectively, were studied for their taxonomic position. On the basis of chemotaxonomic data [i.e. major ubiquinone (Q-10), major polar lipids (phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine) and major fatty acids (C(18 : 1)omega7c and C(19 : 0) cyclo omega8c)] and 16S rRNA gene sequence similarity, both strains belong to the Alphaproteobacteria. The presence of spermidine and putrescine as the predominant polyamines in CCUG 46016(T) were in agreement with its phylogenetic affiliation in the vicinity of the genus Ochrobactrum. 16S rRNA gene sequence similarities between both strains and established species within the genera Bartonella, Ochrobactrum and Brucella were less than 95 %. Although both organisms showed highest 16S rRNA gene sequence similarity to members of Brucella, phenotypic features (including chemotaxonomic features) were more like those of members of the genus Ochrobactrum. Sequence comparison of the recA genes confirmed the separate phylogenetic position of the two strains. On the basis of DNA-DNA pairing results and physiological and biochemical data, the two strains can be clearly differentiated from each other and from all known Ochrobactrum species. It is evident that these organisms represent two novel species in a new genus, Pseudochrobactrum gen. nov., for which the names Pseudochrobactrum asaccharolyticum sp. nov. (the type species, type strain CCUG 46016(T)=CIP 108977(T)) and Pseudochrobactrum saccharolyticum sp. nov. (type strain CCUG 33852(T)=CIP 108976(T)) are proposed.

Adhesives↗
PubMed2004

Occurrence and potential diagnostic applications of serological cross-reactivities between Brucella and other alpha-proteobacteria.

Agrobacterium, Sinorhizobium, and Ochrobactrum are genera closely related to Brucella but, in contrast to the latter, are not pathogenic for humans and animals. We studied by an indirect enzyme-linked immunosorbent assay (ELISA) the reactivities of brucellosis sera against cytosolic (CYT) and membrane (MA) antigens from these nonpathogenic bacteria, and we evaluated the potential usefulness of these cross-reactions for the diagnosis of brucellosis in humans, sheep, cows, and dogs. Canine infection by Brucella canis was detected with high specificity by CYT antigen-based ELISAs (96% for Agrobacterium, 96% for Sinorhizobium, and 91% for Ochrobactrum), while sensitivity was variable (58% for Agrobacterium, 88% for Sinorhizobium, and 84% for Ochrobactrum). In addition, it was possible to diagnose canine disease shortly after exposure to the pathogen (15 days). Similar results for canine brucellosis were obtained with MA antigens. In contrast, normal sera from humans, sheep, and cattle reacted strongly with all the antigens (CYT and MA antigens from the three bacteria), producing high cutoff values and, consequently, low sensitivities. While for some host species the reactivity patterns of normal sera by Western blotting were similar to those produced with sera from infected individuals, the reactivity pattern of bovine sera against Sinorhizobium meliloti antigens exhibited some differential bands for the two groups of sera. These results show that crude fractions from nonpathogenic alpha-proteobacteria can be used to diagnose canine brucellosis but may need to be further separated into simpler fractions to have diagnostic usefulness in ovine, bovine, or human infection. By reducing the biosafety requirements, the use of antigens derived from these nonpathogenic bacteria would simplify the production of diagnostic kits for brucellosis, especially in settings where biosafety level-3 facilities are scarce or absent.

Alphaproteobacteria↗
PubMed2004

Bacterial reduction of toxic Cr (VI) into Cr (III).

Two chromium-resistant bacterial strains CrT-1 and CrT-13, which can tolerate K2CrO4 up to 40 mg x mL(-1) on nutrient agar, 25 mg x mL(-1) K2 CrO4 in nutrient broth, and up to 10 mg x mL(-1) in acetate-minimal media, were used in this study. On the basis of 16S rRNA, strain CrT-1 was identified as Ochrobactrum intermedium and CrT-13 as Brevibacterium sp.. Uptake of chromate was greater in living cells than in heat-killed cells. Ochrobactrum intermedium CrT-1 reduced 73% and 41% of Cr(V) while Brevibacterium CrT-13 reduced 62% and 48% Cr(VI) at an initial chromate concentration of 750, and 1500 microg x mL(-1), after 96 hours with an inoculum size of 9.6 x 10(7) cells mL(-1). Different heavy metals at low concentrations did not affect the reduction potential of the strains significantly. Ochrobactrum intermedium CrT-1 reduced 84% and 65% while Brevibacterium CrT-13 reduced 60% and 44% of Cr(VI) at an initial Cr(VI) concentration of 250 and 500 microg x mL(-1), respectively, in an industrial effluent sample.

Bacteria↗
PubMed2004

Interaction of endotoxins with Toll-like receptor 4 correlates with their endotoxic potential and may explain the proinflammatory effect of Brucella spp. LPS.

Endotoxins displaying differences in the chemical structure of their lipid A were used to induce the expression of chemokines in the human monocytic THP-1 cell line. LPS from two enterobacterial species such as Escherichia coli and Yersinia enterocolitica induced mRNA expression of IFN-gamma-inducible protein (IP)-10, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta, monocyte chemoattractant protein (MCP)-1 and IL-8. LPS from the non-enterobacterial genera Brucella and Ochrobactrum induced the expression of these chemokines to a lower extent. Attempts to address the signaling routes involved in these responses were carried out in transiently transfected HEK293 cells. Induction of kappaB-driven transcriptional activity by enterobacterial LPS was observed in cells transfected with TLR-4 alone, although co-transfection of TLR-4, MD-2 and CD14 provided optimal induction. The response to Brucella spp. and Ochrobactrum anthropi LPS was only significant at the concentration of 10 microg/ml. These data indicate that LPS from Brucella spp. and O. anthropi, which contain lipid A moieties with structural features different from those of Enterobacteriaceae elicit biochemical signaling via TLR-4 only at high concentrations. Neither TLR-1, TLR-2 and TLR-6 nor heterodimeric combinations of these receptor molecules are involved. Conversely, the ability of LPS to activate the TLR-4 route is a reliable molecular biomarker for endotoxicity.

Animals↗
PubMed2006

Evaluation of significance of bacteria in larval development of Cochliomyia macellaria (Diptera: Calliphoridae).

Bacteria were isolated and identified from the digestive tract of the secondary screwworm, Cochliomyia macellaria (F.) (Diptera: Calliphoridae), and their role in the larval development of this insect was assessed in laboratory bioassays. The analysis of 16S rDNA sequences revealed that the bacterial isolates represented four species: Providencia sp., Escherichia coli O157:H7 (Escherich), Enterococcus faecalis (Orla-Jensen), and Ochrobactrum sp. (Holmes). Developmental assays demonstrated that C. macellaria larvae are able to develop on a sterile blood agar, and no bacteria are required to complete larval development. Indeed, developmental times were shorter and survival rates of C. macellaria on a sterile blood agar and the modified Harris rearing diet were greater compared with that on the blood agar inoculated with individual and mixed bacterial isolates. The cultures of Ochrobactrum sp. and E. faecalis supported larval development to a significantly greater extent than those of Providencia sp. and E. coli O157:H7. The presence of bacteria in newly emerged C. macellaria adults also was assessed and revealed that the bacteria in the gut of larvae can survive pupation and colonize the gut of adult flies. This study shows that development of larvae of C. macellaria does not depend on bacteria and that some bacterial isolates negatively impact larval development.

Analysis of Variance↗