排序方式: 共有5条查询结果,搜索用时 487 毫秒
1
1.
Estimates of protozoan- and viral-mediated mortality of bacterioplankton in Lake Bourget (France) 总被引:2,自引:0,他引:2
STÉPHAN JACQUET ISABELLE DOMAIZON SÉBASTIEN PERSONNIC ANGIA SRIRAM PRADEEP RAM MIKAL HEDAL SOLANGE DUHAMEL TÉLESPHORE SIME-NGANDO 《Freshwater Biology》2005,50(4):627-645
1. We performed three, 1‐week in situ experiments in March‐April (expt 1), May (expt 2) and August (expt 3) 2003 in order to assess protozoan and virus‐induced mortality of heterotrophic bacteria in a French lake. Viral and bacterial abundances were obtained using flow cytometry (FCM) while protozoa were counted using epifluorescence microscopy (EFM). 2. A dilution approach, applied to pretreated grazer‐free samples, allowed us to estimate that viral lysis could be responsible for 60% (expt 1), 35% (expt 2) and 52% (expt 3) of daily heterotrophic bacterial mortality. Flagellate (both mixotrophic and heterotrophic) grazing in untreated samples, was responsible for 56% (expt 1), 63% (expt 2) and 18% (expt 3) of daily heterotrophic bacteria removal. 3. These results therefore suggest that both viral lysis and flagellate grazing had a strong impact on bacterial mortality, and this impact varied seasonally. 4. From parallel transmission electron microscopy (TEM) analysis, we found that the burst size (i.e. the number of viruses potentially released per lysed cell) ranged from nine to 25 (expt 1), 10 to 35 (expt 2) and eight to 25 (expt 3). The percentage of infected heterotrophic bacteria was 5.7% (expt 1), 3.4% (expt 2) and 5.7% (expt 3) so that the calculated percentage of bacterial mortality induced by viruses was 6.3% (expt 1), 3.7% (expt 2) and 6.3% (expt 3). 5. It is clear that the dilution‐FCM and TEM methods yielded different estimates of viral impact, although both methods revealed an increased impact of viruses during summer. 相似文献
2.
Breeding season and clutch size of Indian passerines 总被引:1,自引:0,他引:1
3.
GOVINDA S. VISVESVARA RAMA SRIRAM YVONNE QVARNSTROM KAKALI BANDYOPADHYAY ALEXANDRE J. DA SILVA NORMAN J. PIENIAZEK GUY A. CABRAL 《The Journal of eukaryotic microbiology》2009,56(4):357-366
ABSTRACT. Paravahlkampfia francinae n. sp., a new species of the free-living amoeba genus Paravahlkampfia , designated as CDC:V595, was isolated from the cerebrospinal fluid of a patient with headache, sore throat, and vomiting, typical symptoms of primary amoebic meningoencephalitis (PAM) caused by Naegleria fowleri . The isolate grew at 33 °C, 37 °C, 40 °C, and 42 °C and destroyed mammalian cell cultures. However, it did not kill young mice upon intranasal inoculation. P. francinae does not produce flagellates and does not grow on agar plates coated with Gram-negative bacteria such as Escherichia coli , the usual food source of Paravahlkampfia ustiana , the type species of the genus. The trophozoite at light microscopy exhibited eruptive locomotion and possessed a single vesicular nucleus. Ultrastructurally, the trophozoites had numerous mitochondria with discoidal cristae but did not have a Golgi apparatus. The trophozoites differentiated into cysts after consuming most of the monolayer. The cyst had an inner well-differentiated endocyst and an outer thin, wrinkled, and wavy ectocyst with no pores. During excystation trophozoites ruptured the cyst wall and emerged from the cysts. A unique feature seen in the cysts was the presence of bacterial endosymbionts, both in the endoplasm and within the cyst wall. Full-length sequencing analysis of the 18S and 5.8S RNA genes of P. francinae showed that they were distinct from those of other Paravahlkampfia species. The patient recovered within a few days indicating that some of the previously reported cases of PAM that survived may have been due to P. francinae . 相似文献
4.
Genetic Variations in the Internal Transcribed Spacer and Mitochondrial Small Subunit rRNA Gene of Naegleria spp. 总被引:1,自引:0,他引:1
LING ZHOU RAMA SRIRAM GOVINDA S. VISVESVARA LIHUA XIAO 《The Journal of eukaryotic microbiology》2003,50(S1):522-526
ABSTRACT: Naegleria spp. are widely distributed free-living amebas, but one species in the genus, N. fowleri , causes acute fulminant primary amebic meningoencephalitis in humans and other animals. Thus, it is important to differentiate N. fowleri from the rest in the genus of Naegleria , and to develop tools for the detection of intra-specific genetic variations. In this study, one isolate each of N. australiensis, N. gruberi, N. jadini , and N. lovaniensis and 22 isolates of N. fowleri were characterized at the internal transcribed spacers (ITS) and mitochondrial small subunit rRNA (mtSSU rRNA) gene. The mtSSU rRNA primers designed amplified DNA of all isolates, with distinct sequences obtained from all species examined. In contrast, the ITS primers only amplified DNA from N. lovaniensis and N. fowleri , with minor sequence differences between the two. Three genotypes of N. fowleri were found among the isolates analyzed in both the mtSSU rRNA gene and ITS. The extent of sequence variation was greater in the mtSSU rRNA gene, but the ITS had the advantage of length polymorphism. These data should be useful in the development of molecular tools for rapid species differentiation and genotyping of Naegleria spp. 相似文献
5.
SADANAND YEWALE ZEBA FARASH SANMAN KOLHE SASIDHARAN SAKKAN SHRINIVAS BHOPE PRADNYA AMBEKAR SRIRAM PADMANABHAN 《Polish journal of microbiology》2020,69(4):453
Stems and roots of Salacia genus plants have been used as a specific remedy for early-stage diabetes, and one of the four sulphonium sulphates, salacinol is the compound responsible for the anti-diabetic activity. Salacia is prone to microbial contamination and insect infestation; hence, methods to estimate the microbial load in such plants will enhance its nutritional value. This paper highlights the novel use of Soleris® to quantify microbes of all types, namely bacteria, yeasts, molds, and coliforms in herbal extracts. The microbial analysis results obtained with Soleris® test vial have been compared with the conventional method, and the results indicate that Soleris® is equally efficient as the conventional method and in fact displays several advantages over the traditional method. The Soleris® method is a real time monitoring system that is highly sensitive, user-friendly, and environmentally friendly since it generates very little biomedical waste and saves a large amount of time. The data presented here demonstrate that for highly contaminated samples, results are available within 24 h. For yeasts and molds, the Soleris® method produces results in 48 h, thus offering considerable time savings compared to other commonly used methods.Key words: Salacia, salacinol, microbial load, bacteria, yeasts, herbals 相似文献
1