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Indicator Strains (indicator + strain)
Selected AbstractsAnalysis of nodulation kinetics in Frankia,Discaria trinervis symbiosis reveals different factors involved in the nodulation processPHYSIOLOGIA PLANTARUM, Issue 4 2008Luciano Andrés Gabbarini The induction of root nodule development in actinorhizal symbiosis would depend on the concentration of factors produced by the bacteria and the plant. A detailed analysis of nodulation description parameters revealed different factors related to the nodulation process. The initial time for nodulation (t0), the initial nodulation rate (v0) and the total time of nodule development (tNOD) were defined and consequently quantified in different experimental conditions: co-inoculation of Discaria trinervis with increasing concentrations of different non-infective bacteria together with the full compatible infective Frankia strain (the indicator strain) used at a limiting concentration or by changing plant factor(s) concentration. All the above nodulation parameters were modified by changing doses of full compatibility infective strain Frankia BCU110501; v0 appears to be an expression of symbiotic recognition between partners as only fully symbiotic indicator Frankia BCU110501 was able to change it; t0 seems not to reflect symbiotic recognition because it can also be modified by non-infective Frankia but suggest the existence of a basic level of plant microbe recognition. The initial time for nodulation t0, reflecting the time required for the early interactions toward nodulation, is an inverse measure of the ability to establish early interactions toward nodulation. The increase in plant factors concentration also reduces t0 values, suggesting that a plant factor is involved and favors very early interactions. Increases in plant factors concentration also modify the final number of nodules per plant and the nodule cluster profile along the taproot as an expression of the autoregulation phenomenon. Meanwhile, Frankia inoculums' concentration, either infective or not, modified tNOD in an opposite way plant factors did. In conclusion, the analysis of nodulation kinetics appears to be an appropriate tool to investigate factors involved in the symbiotic interaction leading to the formation of nitrogen-fixing nodules. [source] Genotoxicity of nitrosulfonic acids, nitrobenzoic acids, and nitrobenzylalcohols, pollutants commonly found in ground water near ammunition facilitiesENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2006Tamara Grummt Abstract 2-Amino-4,6-dinitrobenzoic acid (2-A-4,6-DNBA), 4-amino-2,6-dinitrobenzoic acid (4-A-2,6-DNBA), 2,4,6-trinitrobenzoic acid (2,4,6-TNBA), 2-amino-4, 6-dinitrobenzylalcohol (2-A-4,6-DNBAlc), 4-amino-2,6-dinitrobenzylalcohol (4-A-2,6-DNBAlc), 2,4-dinitrotoluol-5-sulfonic acid (2,4-DNT-5-SA), 2,4-dinitrotoluol-3-sulfonic acid (2,4-DNT-3-SA), and 2, 4-dinitrobenzoic acid (2,4-DNBA) are derivatives of nitro-explosives that have been detected in groundwater close to munitions facilities. In the present study, the genotoxicity of these compounds was evaluated in Salmonella/microsome assays (in strains TA100 and TA98, with and without S9 and in TA98NR without S9), in chromosomal aberration (CA) tests with Chinese hamster fibroblasts (V79), and in micronucleus (MN) assays with human hepatoma (HepG2) cells. All compounds except the sulfonic acids were positive in the bacterial mutagenicity tests, with 2,4,6-TNBA producing the strongest response (8023 revertants/,mol in TA98 without S9 activation). 2-A-4,6-DNBA was a direct acting mutagen in TA98, but negative in TA100. The other positive compounds were ,1,3 orders of magnitude less mutagenic than 2,4,6-TNBA in TA98 and in TA100; relatively strong effects (,50,400 revertants/,mol) were produced by the benzylacohols in the two indicator strains. With the exception of 2,4-DNBA, the mutagenic responses were lower in the nitroreductase-deficient strain TA98NR than in the parental strain. 2,4-DNBA produced a marginally positive response in the V79-cell CA assay; the other substances were devoid of activity. Only the benzoic acids were tested for MN induction in HepG2 cells, and all produced positive responses. As in the bacterial assays, the strongest effect was seen with 2,4,6-TNBA (significant induction at ,1.9 ,M). 4-A-2,6-DNBA was positive at 432 ,M; the weakest effect was observed with 2,4,-DNBA (positive at ,920 ,M). The differences in the sensitivity of the indicator cells to these agents can be explained by differences in the activities of enzymes involved in the activation of the compounds. The strong responses produced by some of the compounds in the human-derived cells suggest that environmental exposure to these breakdown products of nitro-explosives may pose a cancer risk in man. Environ. Mol. Mutagen., 2006. © 2005 Wiley-Liss, Inc. [source] Assessment of survival of Listeria monocytogenes, Salmonella Infantis and Enterococcus faecalis artificially inoculated into experimental waste or compostJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2010N. Paniel Abstract Aims:, To evaluate survival of pathogenic strains, Listeria monocytogenes and Salmonella Infantis and a sanitation indicator Enterococcus faecalis in composts at different stages of the composting process and during storage. Methods and Results:, The studied pathogenic and indicator strains, originally isolated from compost, were inoculated into compost samples from the various stages of the composting process. During incubation, indigenous microflora diversity was monitored with DGGE analysis. After 90 days of incubation, strain survival was observed in compost sampled before the beginning of the cooling phase, and DGGE analysis demonstrated an increase of microbial diversity up to the cooling phase. However, inoculated strains were not detected in composts after 30, 60 or 90 days of incubation in compost sampled after the start of the cooling phase. Microbial diversity also became stable, and DGGE profiles reached a maximum number of bands at this stage. Conclusions:, Strain survival was not observed in stabilized composts. The cooling phase seems to be the turning point for pathogen survival and at this stage the indigenous microflora appeared to play a significant role in suppression. Significance and Impact of the Study:, The importance of indigenous microflora in the survival of pathogens in four different composts was demonstrated. Stabilized composts were recommended for spreading on land. [source] Identification and production of a bacteriocin from Enterococcus mundtii QU 2 isolated from soybeanJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2005T. Zendo Abstract Aims:, Identification of the bacteriocin produced by Enterococcus mundtii QU 2 newly isolated from soybean and fermentative production of the bacteriocin. Methods and Results:, The bacteriocin produced by Ent. mundtii QU 2 inhibited the growth of various indicator strains, including Enterococcus, Lactobacillus, Leuconostoc, Pediococcus and Listeria. The bacteriocin activity was stable at wide pH range and against heat treatment, but completely abolished by proteolytic enzymes. The bacteriocin was purified from the culture supernatant by the three-step chromatographic procedure. Mass spectrometry, amino acid sequencing and DNA sequencing revealed that the bacteriocin was similar to class IIa bacteriocins produced by other Ent. mundtii strains. The bacteriocin production decreased in the absence of glucose, nitrogen sources, or Tween 80 in MRS medium. Additionally, it was strongly suppressed by addition of Ca2+ (CaCO3 or CaCl2). In pH-controlled fermentations, the highest bacteriocin production was achieved at pH 6·0, whereas the highest cell growth was obtained at pH 7·0. Conclusions:,Ent. mundtii QU 2 produced a class IIa bacteriocin. Some growth factors (e.g. Ca2+ and pH) influenced the bacteriocin production. Significance and Impact of the Study:, A new soybean isolate, Ent. mundtii QU 2 was found to be a class IIa bacteriocin producer. Factors influencing the bacteriocin production described herein are valuable for applications of the bacteriocins from Ent. mundtii strains. [source] A 76-residue polypeptide of colicin E9 confers receptor specificity and inhibits the growth of vitamin B12 -dependent Escherichia coli 113/3 cellsMOLECULAR MICROBIOLOGY, Issue 3 2000Christopher N. Penfold The mechanism by which E colicins recognize and then bind to BtuB receptors in the outer membrane of Escherichia coli cells is a poorly understood first step in the process that results in cell killing. Using N- and C-terminal deletions of the N-terminal 448 residues of colicin E9, we demonstrated that the smallest polypeptide encoded by one of these constructs that retained receptor-binding activity consisted of residues 343,418. The results of the in vivo receptor-binding assay were supported by an alternative competition assay that we developed using a fusion protein consisting of residues 1,497 of colicin E9 fused to the green fluorescent protein as a fluorescent probe of binding to BtuB in E. coli cells. Using this improved assay, we demonstrated competitive inhibition of the binding of the fluorescent fusion protein by the minimal receptor-binding domain of colicin E9 and by vitamin B12. Mutations located in the minimum R domain that abolished or reduced the biological activity of colicin E9 similarly affected the competitive binding of the mutant colicin protein to BtuB. The sequence of the 76-residue R domain in colicin E9 is identical to that found in colicin E3, an RNase type E colicin. Comparative sequence analysis of colicin E3 and cloacin DF13, which is also an RNase-type colicin but uses the IutA receptor to bind to E. coli cells, revealed significant sequence homology throughout the two proteins, with the exception of a region of 92 residues that included the minimum R domain. We constructed two chimeras between cloacin DF13 and colicin E9 in which (i) the DNase domain of colicin E9 was fused onto the T+R domains of cloacin DF13; and (ii) the R domain and DNase domain of colicin E9 were fused onto the T domain of cloacin DF13. The killing activities of these two chimeric colicins against indicator strains expressing BtuB or IutA receptors support the conclusion that the 76 residues of colicin E9 confer receptor specificity. The minimum receptor-binding domain polypeptide inhibited the growth of the vitamin B12 -dependent E. coli 113/3 mutant cells, demonstrating that vitamin B12 and colicin E9 binding is mutually exclusive. [source] Mutacin production in Streptococcus mutans genotypes isolated from caries-affected and caries-free individualsMOLECULAR ORAL MICROBIOLOGY, Issue 1 2005R. U. Kamiya Relationships between genetic diversity and mutacin production in Streptococcus mutans were evaluated in 319 clinical isolates from eight caries-affected and eight caries-free individuals. The isolates were submitted to mutacin typing and AP-PCR (arbitrarily primed polymerase chain reaction) assay. The mutacin production was detected for 12 Streptococcus sp. indicator strains. Results showed significant variations in the mutacin production profiles and the inhibitory spectra of both groups. A possible association was seen between mutacin activity and the distinct patterns of Streptococcus sp. colonization in the two groups. Genotyping by AP-PCR using the primers OPA-02 and OPA-13 revealed 101 distinct genotypes against 48 phenotypes identified by mutacin typing. No correlation was observed between the inhibitory spectra of mutacin and genotypic similarities based on AP-PCR analyses. According to our results, strains of the same S. mutans genotype showed different mutacin profiles, suggesting a high degree of interstrain diversity. In conclusion, mutacin production seems to be of clinical importance in the colonization of S. mutans and is highly diversified in the S. mutans species. [source] Determination of mutacin activity and detection of mutA genes in Streptococcus mutans genotypes from caries-free and caries-active childrenMOLECULAR ORAL MICROBIOLOGY, Issue 3 2003P. L. Longo Relationships between genetic diversity, mutacin production and sensitivity to mutacins in Streptococcus mutans were evaluated in 19 clinical isolates from caries-free and caries-active children. Mutacin production was tested against 30 indicator strains; results showed significant variations in the inhibitory spectra of the clinical isolates. There was no association between the inhibitory spectrum of the infecting strain and the caries experience or the level of mutans streptococci infection of the host. Homology to the mutA gene coding for mutacin II was detected in one clinical isolate; none of the clinical isolates showed homology to the mutA genes coding for mutacins I or III. Genotyping by random amplified polymorphic DNA (RAPD) reactions grouped the isolates into three clusters, but no correlation was found between any of the clusters and mutacin activity, caries experience or level of mutans streptococci in the host. [source] | ||||||||||