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1.
Graves AK Liwimbi L Israel DW van Heugten E Robinson B Cahoon CW Lubbers JF 《Folia microbiologica》2011,56(2):131-137
The prevalence of ten antibiotic resistance genes (ARGs) was evaluated in a total of 616 Escherichia coli isolates from swine manure, swine lagoon effluent, and from soils that received lagoon effluent on a commercial swine farm
site in Sampson County, North Carolina (USA). Isolates with ARGs coding for streptomycin/spectinomycin (aadA/strA and strB), tetracycline (tetA and tetB), and sulfonamide (sul1) occurred most frequently (60.6–91.3%). The occurrence of E. coli isolates that carried aadA, tetA, tetB, and tetC genes was significantly more frequent in soil samples (34.0–97.2%) than in isolates from lagoon samples (20.9–90.6%). Furthermore, the frequency of isolates that contain genes coding
for aadA and tetB was significantly greater in soil samples (82.6–97.2%) when compared to swine manure (16.8–86.1%). Isolates from the lagoon
that carried tetA, tetC, and sul3 genes were significantly more prevalent during spring (63.3–96.7%) than during winter (13.1–67.8%). The prevalence of isolates
from the lagoon that possessed the strA, strB, and sul1 resistance genes was significantly more frequent during the summer (90.0–100%) than during spring (66.6–80.0%). The data
suggest that conditions in the lagoon, soil, and manure may have an impact on the occurrence of E. coli isolates with specific ARGs. Seasonal variables seem to impact the recovery isolates with ARGs; however, ARG distribution
may be associated with mobile genetic elements or a reflection of the initial numbers of resistant isolates shed by the animals. 相似文献
2.
The first establishment of a homologous expression system in the host Ralstonia pickettii CGMCC1596 using the compatible broad-host-range plasmid pWB5 is described. When whole cells of the recombinant strain R. pickettii MMYY01 (CGMCC1596/pYY05) were used as the biocatalyst to transform dl-4-hydroxyphenylhydantoin (dl-HPH) to d-4-hydroxyphenylglycine (d-HPG), the conversion rate reached 94 % in first 9 h, at a production rate of 2.8 g L−1 h−1, with the rapid reduction of the intermediate [N-carbamoyl-2-(4-hydroxyphenyl)glycine], compared with 80 % in >50 h at a rate of 0.5 g L−1 h−1 for the CGMCC1596. The stability of the recombinant plasmid pYY05 is sufficient for its application in industrial batch fermentation.
An alternative strategy for the conversion of dl-HPH to d-HPG by resting CGMCC1596 cells and heterologous DCase expressed by E. coli is discussed. 相似文献
3.
Genetic variability among 122 Rhynchosporium secalis isolates collected from barley in three regions of Tunisia was investigated using host differentials, amplified fragment
length polymorphism (AFLP), and microsatellite markers. The isolates were collected from a widely grown scald-susceptible
barley cultivar Rihane and a range of local landrace cultivars in geographically distinct regions with different agroclimatic
conditions. Pathotypic diversity (the proportion of unique pathotypes) was high in R. secalis populations from the high (100% diversity), moderate (95%), and low (100%) rainfall areas of Tunisia, and from both Rihane
(which is the sole variety grown in the high rainfall region) and local landraces (which predominate in the low rainfall area).
This may reflect a general adaptability for aggressiveness and suggests that the widely grown cultivar Rihane has exerted
little or no selection pressure on the pathogen population since its release in 1983. Genotypic diversity (GD), defined as
the probability that two individuals taken at random had different genotypes, was high for populations from Rihane, local
landraces, and different agro-ecological zones (GD = 0.96–0.99). There was low genetic differentiation among pathogen populations
from different host populations (G
ST ≤ 0.08, θ ≤ 0.12) and agro-ecological zones (G
ST ≤ 0.05, θ ≤ 0.04), which may be partly explained by gene flow due to the movement of infected stubble around the country.
There was no correlation (r = 0.06, P = 0.39) between virulence phenotype and AFLP haplotype. A phenetic tree revealed groups with low bootstrap values that did
not reflect the grouping of isolates based on host, pathotype, or agro-ecological region. The implications of these findings
for R. secalis evolutionary potential and scald-resistance breeding in Tunisia are discussed. 相似文献
4.
Subramaniam Gopalakrishnan Pagidi Humayun Bandru Keerthi Kiran Iyer Girish Kumar Kannan Meesala Sree Vidya Kanala Deepthi Om Rupela 《World journal of microbiology & biotechnology》2011,27(6):1313-1321
A total of 360 bacteria, isolated from the rhizospheres of a system of rice intensification (SRI) fields, were characterized
for the production of siderophore, fluorescence, indole acetic acid (IAA), hydrocyanic acid (HCN) and solubilization of phosphorus.
Of them, seven most promising isolates (SRI-156, -158, -178, -211, -229, -305 and -360) were screened for their antagonistic
potential against Macrophomina phaseolina (causes charcoal rot in sorghum) by dual culture assay, blotter paper assay and in greenhouse. All the seven isolates inhibited
M. phaseolina in dual culture assay, whereas six isolates solubilized phosphorous (except SRI-360), all seven produced siderophore, four
produced fluorescence (except SRI-178, -229 and -305), six produced IAA (except SRI-305) and five produced HCN (except SRI-158
and -305). In the blotter paper assay, no charcoal rot infection was observed in SRI-156-treated sorghum roots, indicating
complete inhibition of the pathogen, while the roots treated with the other isolates showed 49–76% lesser charcoal rot infection
compared to the control. In the antifungal activity test (in green house on sorghum), all the isolates increased shoot dry
mass by 15–23% and root dry mass by 15–20% (except SRI-158 and -360), over the control. In order to confirm the plant growth-promoting
(PGP) traits of the isolates, the green house experiment was repeated but, in the absence of M. phaseolina. The results further confirmed the PGP traits of the isolates as evidenced by increases in shoot and root dry mass, 22–100%
and 5–20%, respectively, over the control. The sequences of 16S rDNA gene of the isolates SRI-156, -158, -178, -211, -229,
-305 and -360 were matched with Pseudomonas
plecoglossicida, Brevibacterium antiquum, Bacillus altitudinis, Enterobacter ludwigii, E. ludwigii, Acinetobacter tandoii and P. monteilii, respectively in BLAST analysis. This study indicates that the selected bacterial isolates have the potential for PGP and
control of charcoal rot disease in sorghum. 相似文献
5.
I. Batarilo G. Maravic-Vlahovicek B. Bedenic S. Kazazic J. Bingulac-Popovic M. Slade-Vitkovic S. Katić I. Jukic 《Letters in applied microbiology》2022,75(1):103-113
This study evaluated antibiotic susceptibility and presence of blaOXA22 and blaOXA60 genes in 81 isolates of Ralstonia pickettii obtained from different purified and ultra-pure water systems in two different geographical areas of Croatia. E-test and disc diffusion test were performed to determine antibiotic susceptibility. Polymerase chain reaction was applied to detect genes encoding OXA-22 and OXA-60 oxacillinases previously identified in R. pickettii. The isolates were genotyped by pulsed-field gel electrophoresis. The results revealed variable susceptibility/resistance profiles. Our isolates exhibited high susceptibility rates to ceftriaxone, cefotaxime, piperacillin-tazobactam, ciprofloxacin, imipenem, cefepime and in lesser extent to ceftazidime. High rates of susceptibility were also observed for sulphamethoxazole-trimethoprim and piperacillin. High resistance rates were noticed for ticarcillin-clavulanate, aztreonam and meropenem, as well as for all aminoglycosides tested. Modified Hodge test was positive in 51·9% strains, indicating production of carbapenemases. blaOXA22 and blaOXA60 genes were detected in 37·0 and 80·3% strains, respectively. Pulsed-field gel electrophoresis identified three major clusters containing subclusters. R. pickettii should be taken seriously as a possible cause of nosocomial infections to ensure adequate therapy, to prevent the development of resistant strains and to try to reduce the possibility of R. pickettii surviving in clean and ultra clean water systems. 相似文献
6.
The aim of this study was to assess the diagnostic properties of the two selective plating media and a chromogenic medium
for identification of Bacillus cereus. The 324 isolates were B. cereus (37%), Bacillus weihenstephanensis (45%) or Bacillus thuringiensis (18%), as identified by a new combination of techniques. All isolates were growing on mannitol–egg yolk–polymyxin agar (MYP),
and they did not form acid from mannitol. However, a significant lower number of B. thuringiensis isolates did not show lecithinase activity. All isolates were also growing on polymyxin–egg yolk–mannitol–bromothymol blue
agar (PEMBA); however, 11% isolates indicated that they did produce acid from mannitol, and 15% isolates did not show any
lecithinase activity. Five of the isolates did not grow at all on the chromogenic agar, and 14 of the growing isolates were
β-glucosidase negative. It is concluded that the two recommended selective plating media MYP and PEMBA for detection of B. cereus group bacteria both have their limitations for identification of some B. cereus, B. weihenstephanensis or B. thuringiensis. However, MYP is preferable compared to PEMBA. The chromogenic medium has its own advantages and limitations, and some of
the limitations seem to be solved by incubation at 30°C instead of the recommended 37°C. 相似文献
7.
Bark beetles are well known vectors of ophiostomatoid fungi including species of Ophiostoma, Grosmannia and Ceratocystis. In this study, the most common ophiostomatoid fungi associated with the lodgepole pine beetle, Dendroctonus murrayanae, were characterized. Pre-emergent and post-attack adult beetles were collected from lodgepole pines at four sites in British
Columbia, Canada. Fungi were isolated from these beetles and identified using a combination of morphology and DNA sequence
comparisons of five gene regions. In all four populations, Grosmannia aurea was the most common associate (74–100% of all beetles) followed closely by Ophiostoma abietinum (29–75%). Other fungi isolated, in order of their relative prevalence with individual beetles were an undescribed Leptographium sp. (0–13%), Ophiostoma ips (0–15%), Ophiostoma piliferum (0–11%), a Pesotum sp. (0–11%) and Ophiostoma floccosum (0–1%). Comparisons of the DNA sequences of Leptographium strains isolated in this study, with ex-type isolates of G. aurea, Grosmannia robusta, Leptographium longiclavatum, and Leptographium terebrantis, as well as with sequences from GenBank, revealed a novel lineage within the Grosmannia clavigera complex. This lineage included some of the D. murrayane isolates as well as several isolates from previous studies referred to as L. terebrantis. However, the monophyly of this lineage is not well supported and a more comprehensive study will be needed to resolve its
taxonomic status as one or more novel taxa. 相似文献
8.
W.E. van de Weg 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):445-451
A gene-for-gene model is postulated to explain the observed interactions between cultivars of strawberry and races of Phytophthora fragariae. Five interacting resistance (R1–R5) and avirulence (Avr1–Avr5) factors explain all the available data involving 15 host
genotypes, including the USA and Canadian differential series, and 12 pathogen isolates from North America. Interactions between
pathogen isolates and UK and German differentials are also explained by the proposed model. The model makes it possible to
develop a universally applicable differential series, to present a systematic, unequivocal nomenclature of races, and to increase
the efficiency of breeding programs.
Received: 26 April 1996 / Accepted: 19 July 1996 相似文献
9.
S. Pažoutová 《Folia microbiologica》2009,54(3):217-229
Genetic variability of Phoma sorghina, a ubiquitous facultative phytopathogen, was investigated on 41 isolates cultivated from surface-sterilized sorghum grains
originating from South Africa and Texas; pearl millet isolates from Namibia were also included. Most of the isolates from
Texas produced intense red pigments, especially on Czapek-Dox agar plates. Many African isolates formed conspicuous dark radial
substrate hyphae with intercalated chlamydospores on oatmeal plates. Conidial dimensions and shape were very variable (mean
lengths 4.5–5.7 μm). Haplotypes were defined based on 53 markers from banding patterns obtained with rep-PCR (primers: M13core,
ERIC IR). The shared geographic origin was partially reflected in the clades of the haplotype phylogram. The values of G
ST were intermediate; 16–37 % of the variation was found between the populations. Nm values of gene flow were 0.84–1.15. Average gene diversity H
E was moderate (0.256). Sequences of ITS-rDNA were obtained from 21 isolates. Allele 1 was found in 9 isolates scattered throughout
the clades, allele 2 occurred in 6 isolates (5 of them from the same clade), alleles 3 and 4 were shared by two isolates each
and two isolates were unique. Alleles 1 and 2 were also found among highly related sequences from GenBank. All shared an 8-bp deletion near the 5′ end of ITS2 that was not found in any other Phoma/Didymella species and which may be a typical marker for P. sorghina. Among related species, members of legume-associated Ascochyta/Didymella complex, Epicoccum spp., D. applanata and P. glomerata were found. 相似文献
10.
A. Čížek M. Dolejská R. Karpíšková D. Dědičová I. Literák 《European Journal of Wildlife Research》2007,53(1):55-60
Salmonella were isolated from black-headed gulls (Larus ridibundus) in six locations in the Czech Republic from 1984 to 2005 (Chropyně and Nymburk in 1984–1986; Nové Mlyny, Bartošovice, and
Hodonín in 1991–1994; and Nové Mlyny, Bartošovice, and Ostrava in 2005). Antimicrobial susceptibility was determined in 12
antimicrobial drugs using disk diffusion. Although 95% of Salmonella isolates (197 out of 207) were pansusceptible, the prevalences of resistance increased significantly from 1 (2%) out of 59
isolates in 1984–1986 and 3 (3%) out of 100 isolates in 1991–1994 to 6 (13%) out of 48 isolates in 2005. Furthermore, in 2005,
two isolates were nalidixic acid-resistant and one isolate was multidrug-resistant Salmonella Typhimurium DT 104. These findings suggest that the occurrence of salmonellae in black-headed gulls depends to a large extent
on the contamination where the gulls feed and possibly reflects the dissemination of these strains among farm animals and
humans. Black-headed gulls may also become infected with resistant Salmonella and thus pose a potential risk of Salmonella contamination of surface water and animal feeds, and consequently dissemination. 相似文献
11.
Sepahvand A Shams-Ghahfarokhi M Allameh A Jahanshiri Z Jamali M Razzaghi-Abyaneh M 《Folia microbiologica》2011,56(6):527-534
In the present study, genetic diversity and mycotoxin profiles of Aspergillus flavus isolated from air (indoors and outdoors), levels (surfaces), and soils of five hospitals in Southwest Iran were examined.
From a total of 146 Aspergillus colonies, 63 isolates were finally identified as A. flavus by a combination of colony morphology, microscopic criteria, and mycotoxin profiles. No Aspergillus parasiticus was isolated from examined samples. Chromatographic analyses of A. flavus isolates cultured on yeast extract–sucrose broth by tip culture method showed that approximately 10% and 45% of the isolates
were able to produce aflatoxin B1 (AFB1) and cyclopiazonic acid (CPA), respectively. Around 40% of the isolates produced sclerotia on Czapek–Dox agar. The isolates
were classified into four chemotypes based on the ability to produce AF and CPA that majority of them (55.5%) belonged to
chemotype IV comprising non-mycotoxigenic isolates. Random amplified polymorphic DNA (RAPD) profiles generated by a combination
of four selected primers were used to assess genetic relatedness of 16 selected toxigenic and non-toxigenic isolates. The
resulting dendrogram demonstrated the formation of two separate clusters for the A. flavus comprised both mycotoxigenic and non-toxigenic isolates in a random distribution. The obtained results in this study showed
that RAPD profiling is a promising and efficient tool to determine intra-specific genetic variation among A. flavus populations from hospital environments. A. flavus isolates, either toxigenic or non-toxigenic, should be considered as potential threats for hospitalized patients due to their
obvious role in the etiology of nosocomial aspergillosis. 相似文献
12.
McAlister MB Kulakov LA O'Hanlon JF Larkin MJ Ogden KL 《Journal of industrial microbiology & biotechnology》2002,29(2):75-82
Bacteria isolated previously from ultrapure water (UPW) systems were examined for their ability to survive in UPW, with the
ultimate goal of elucidating potential carbon and energy sources for the bacteria. Two strains of Ralstonia pickettii isolated from different areas within the UPW system (pretreatment and polishing loop, and referred to as strains 3A1 and
MF254A, respectively) and a strain of Bradyrhizobium sp. were compared to increase our understanding of the fundamental behavior of bacteria contaminating UPW. R. pickettii (3A1) grew significantly slower in R2A medium, with a final cell yield much lower than the isolate from the polishing loop.
In addition, R. pickettii MF254A showed a broader substrate range than either strain 3A1 or Bradyrhizobium sp. In UPW, there appears to be a threshold cell concentration (approximately 106 colony-forming units/ml), whereby the cell numbers remain constant for a prolonged period of 6 months or more. Below this
concentration, rapid proliferation is observed until the threshold concentration is attained. Preliminary experiments suggested
that nitrogen gas (frequently added to UPW storage tanks) may contribute to growth of Bradyrhizobium sp. Above the threshold concentration, the strain of Ralstonia sp. isolated from the polishing loop was capable of cryptic growth with heat-killed cells in UPW. However, cryptic growth
was not observed when the cells supplied as nutrients were killed using UV254 light. Furthermore, cryptic growth did not appear
to contribute significantly to proliferation of Bradyrhizobium sp. or Ralstonia sp. 3A1 (isolated from the pretreatment loop). We believe that cryptic growth may aid survival of the bacteria in UPW, but
further experiments are warranted to prove this phenomenon conclusively. Journal of Industrial Microbiology & Biotechnology (2002) 29, 75–82 doi:10.1038/sj.jim.7000273
Received 23 January 2002/ Accepted in revised form 29 April 2002 相似文献
13.
Besma Sghaier-Hammami Inmaculada Redondo-López Ana M. Maldonado-Alconada Sira Echevarría-Zomeño Jesús V. Jorrín-Novo 《Acta Physiologiae Plantarum》2012,34(3):905-922
The present work is directed at studying changes at the proteome level in Arabidopsis thaliana leaves in response to Pseudomonas syringae virulent (Pst) and avirulent (Pst avrRpt2) strains. Arabidopsis leaves were sampled from challenged plants at 4, 8 and 24 h post inoculation. Proteins were TCA–acetone–phenol
extracted and subjected to 2-DE (5–8 pH range) and MS/MS (MALDI–TOF–TOF) analysis. Out of 800 matched spots on each of the
36 gels analysed, 147 spots were either absent in at least one of the conditions studied (time or treatments; qualitative
variable spots) or differentially accumulated between time and treatments (quantitative variable spots). Out of the 24 proteins
successfully identified over TAIR10 database, 23 have not been reported previously in similar proteomics studies of the Arabidopsis thaliana–Pseudomonas syringae interaction. The exhaustive statistical analysis performed, including principal component and heat map, showed that 24 h
post inoculation can clearly discriminate the challenged plants from the control. The protein change occurred early (4 h post
inoculation) following the virulent pathogen infection, whereas the change occurred later (24 h post inoculation) following
the avirulent pathogen inoculation. Concerning the variable proteins, three behavioural groups can be observed: group 1 (common
protein changes in response to virulent and avirulent pathogen infection), group 2 (protein changes in response to virulent
pathogen infection) and group 3 (protein changes in response to avirulent pathogen infection). Differential identified proteins
following the pathogen infection belonged to different groups including those of oxidative stress defence, enzymes of metabolic
pathways and molecular chaperones. 相似文献
14.
Bremia lactucae Regel (Chromista, Peronosporaceae) is an economically destructive pathogen, which causes downy mildew disease on lettuce
(Lactuca sativa L.) worldwide. The ribosomal internal transcribed spacer (ITS) of Bremia lactucae isolates was analyzed for the first time. The ITS region of lettuce downy mildew was observed to have a size of 2458 bp;
thereby, having one of the longest ITS sizes recorded to date. The majority of the extremely large sized ITS2 length of 2086
was attributed to the additional presences of nine repetitive elements with lengths of 179–194 bp, which between them shared
the low homology of 48–69%. Comparison of the ITS2 sequences with the B. lactucae isolates from other host plants showed that isolates present on Lactuca sativa were distinct from those on L. indica var. laciniata, as well as Hemistepta and Youngia. We suggest the high degree of sequence heterogeneity exhibited in the ITS2 region of B. lactucae may warrant the specific detection and diagnosis of this destructive pathogen or its division into several distinct species. 相似文献
15.
To investigate the biocontrol effectiveness of the antibiotic producing bacterium, Pseudomonas aureofaciens 63–28 against the phytopathogen Rhizoctonia solani AG-4 on Petri plates and in soybean roots, growth response and induction of PR-proteins were estimated after inoculation
with P. aureofaciens 63–28 (P), with R. solani AG-4 (R), or with P. aureofaciens 63–28 + R. solani AG-4 (P + R). P. aureofaciens 63–28 showed strong antifungal activity against R. solani AG-4 pathogens in Petri plates. Treatment with P. aureofaciens 63–28 alone increased the emergence rate, shoot fresh weight, shoot dry weight and root fresh weight at 7 days after inoculation,
when compared to R. solani AG-4; P + R treatment showed similar effects. Peroxidase (POD) and β-1,3-glucanase activity of P. aureofaciens 63–28 treated roots increased by 41.1 and 49.9%, respectively, compared to control roots. POD was 26% greater in P + R treated
roots than R. solani treated roots. Two POD isozymes (59 and 27 kDa) were strongly induced in P + R treated roots. The apparent molecular weight
of chitinase from treated roots, as determined through SDS-PAGE separation and comparison with standards, was about 29 kDa.
Five β-1,3-glucanase isozymes (80, 70, 50, 46 and 19 kDa) were observed in all treatments. These results suggest that inoculation
of soybean plants with P. aureofaciens 63–28 elevates plant growth inhibition by R. solani AG-4 and activates PR-proteins, potentially through induction of systemic resistance mechanisms. 相似文献
16.
17.
Waldina P. Reyes-Velázquez Rosa M. Figueroa-Gómez Mauricio Barberis María Marta Reynoso Federico G. A. Rojo Sofía N. Chulze Adriana M. Torres 《Mycotoxin Research》2011,27(3):187-194
Fusarium species can produce fumonisins (FBs), fusaric acid, beauvericin (BEA), fusaproliferin (FUS) and moniliformin. Data on the
natural occurrence of FBs have been widely reported, but information on BEA and FUS in maize is limited. The aims of this
study were to establish the occurrence of Fusarium species in different maize hybrids in Mexico, to determine the ability of Fusarium spp. isolates to produce BEA, FUS and FBs and their natural occurrence in maize. Twenty-eight samples corresponding to seven
different maize hybrids were analyzed for mycobiota and natural mycotoxin contamination by LC. Fusarium verticillioides was the dominant species (44–80%) followed by F. subglutinans (13–37%) and F. proliferatum (2–16%). Beauvericin was detected in three different hybrids with levels ranging from 300 to 400 ng g−1, while only one hybrid was contaminated with FUS (200 ng g−1). All samples were positive for FB1 and FB2 contamination showing levels up to 606 and 277 ng g−1, respectively. All F. verticillioides isolates were able to produce FB1 (13.8–4,860 μg g−1) and some also produced FB2 and FUS. Beauvericin, FUS, FB1 and FB2 were produced by several isolates including F. proliferatum and F. subglutinans and co-production was observed. This is the first report on the co-occurrence of these toxins in maize samples from Mexico.
The analysis of the presence of multiple mycotoxins in this substrate is necessary to understand the significance of these
compounds in the human and animal food chains. 相似文献
18.
Young-hee Jin Young-hee Oh Ji-hun Jung Soo-jin Kim Jin-ah Kim Ki-young Han Min-young Kim Seog-gee Park Young-ki Lee 《Journal of microbiology (Seoul, Korea)》2010,48(2):236-242
A total of 66 Shigella sonnei isolates from 1999 to 2008 in Seoul was analyzed for their antimicrobial resistance, carriage of integron, and the patterns
of Pulsed-field gel electrophoresis (PFGE). A high level of antimicrobial resistance to streptomycin (100%), trimethoprim/sulfamethoxazole
(95%), tetracycline (94%), nalidixic acid (65%), and ampicillin (41%) was observed among S. sonnei isolates. Fourteen profiles of antimicrobial resistance were identified with the most common resistance profile being nalidixic
acid, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole (35%). PCR and DNA sequencing analysis revealed the presence
of class 2 integron in all isolates, and class 1 and 2 integrons in 7 isolates. The class 2 integron carried two types of
gene cassettes. One cassette array was dfrI, sat2, and aadA1 (91%), and the other was dfr1 and sat1 (8%). dfrA12 and aadA2 gene cassette was found in one isolate containing class 1 integron. PFGE was carried out to examine the genetic relatedness
among isolates. All isolates except for one showed similar PFGE patterns (similarity of 80.1%). These results suggest that
the S. sonnei isolated during 1999–2008 in Seoul have similar lineages that have not undergone evolutionary changes with time. 相似文献
19.
I. A. Bryantseva T. P. Tourova O. L. Kovaleva N. A. Kostrikina V. M. Gorlenko 《Microbiology》2010,79(6):780-790
Two strains of purple sulfur bacteria of the family Ectothiorhodospiraceae were isolated from moderately saline steppe lakes (with pH above 9.0) of the Transbaikal region (strain B7-7) and Mongolia
(strain M10). The cells of the novel strains were spiral-shaped, 2.0–3.2 × 9.6–20.0 μm, motile due to a polar tuft of flagella.
Photosynthetic pigments were represented by bacteriochlorophyll a and carotenoids of the spirilloxanthin series. Photosynthetic membranes were represented by long strands of lamellae distributed
throughout the whole cell; unlike most Ectothiorhodospiraceae species, the membranes were not packed into regular stacks. Bacteria were capable of weak growth on sulfide and slow grow
on hydrogen under photoautotrophic conditions. The best growth was noted on sulfide in the presence of acetate and bicarbonate.
Thiosulfate did not stimulate phototrophic growth, even in the presence of organic substrates. The new isolates were alkaliphiles
growing at a pH optimum of 9–10. Growth was possible within a salinity range of 0–80 g/l NaCl, with an optimum at 5–15 g/l
NaCl. The morphology, the structure of the photosynthetic apparatus (strands of lamellae), and the physiology of the new strains
were similar to those of Thiorhodospira sibirica. However, analysis of the 16S rRNA gene sequences demonstrated that the studied isolates were closely related to the type
strain Ectothiorhodospira shaposhnikovii (99% similarity) of the family Ectothiorhodospiraceae, whereas the level of similarity between the new strains and Thiorhodospira sibirica was only 94–95%. According to the results of DNA-DNA hybridization, the DNA-DNA homology level between the tested strains
was almost 100%; the similarity between the new isolates and the type strain Ectothiorhodospira shaposhnikovii was only 58%. The isolates differed from other representatives of the genus Ectothiorhodospira in the structure of the gene encoding the key enzyme of autotrophic CO2 fixation, ribulose-1,5-bisphosphate carboxylase (RuBisCo), which was similar to the RuBisCo genes of members of another family
of sulfur bacteria, Chromatiaceae. The new isolates of purple bacteria were described as a new species of the genus Ectothiorhodospira, Ect. magna sp. nov. with the type strain B7-7T (= VKM B-2537 = DSM 22250). 相似文献
20.
Candidaemias account for 10–20% of nosocomial bloodstream infections depending on the study. Whilst Candida albicans remains the most frequently isolated species, Candida glabrata may be responsible for as many as 10–25% of all candidaemias. Moreover, C. glabrata is generally less susceptible to the azole antifungals than the majority of other pathogenic yeast species. Thus, a rapid
test for the specific identification of isolates of C. glabrata would be useful for patient management if it could be performed at point of isolation, on primary cultures grown on standard
mycological media directly from patient specimens. Under certain conditions, C. glabrata rapidly hydrolyses trehalose into glucose. The GLABRATA RTT kit allows detection of the preformed enzyme responsible for
this action. This study has assessed GLABRATA RTT as an identification tool specifically at point of isolation. Sixty test
isolates were evaluated: 39 clinical isolates of C. glabrata identified at the UK Mycology Reference Laboratory, examples of the recently described genetic relatives of C. glabrata, Candida nivariensis (n = 6) and Candida bracarensis (n = 1), and a selection of other common pathogenic yeast species (n = 14). The test provided results within 30 min. Although 77% (30/39) of confirmed C. glabrata isolates were correctly identified by GLABRATA RTT (positive trehalase test), 23% (9/39) of isolates gave negative or equivocal
results. All other yeast species gave negative results. The performance of GLABRATA RTT in this study is compared to previous
evaluations of the test which employed isolates pre-cultured on specialised media and to other existing conventional identification
methodologies. 相似文献