Search results for "microbiology"
showing 10 items of 7546 documents
Biodiversity and technological potential of wild lactic acid bacteria from raw cows' milk
2009
To study lactic acid bacteria (LAB) biodiversity and to evaluate their potential for use in dairy applications, eight raw cows' milk batches were sampled from five dairy factories located in different areas of the Trentino region during winter and summer milkings. A total of 370 (Gram-positive and catalase-negative) isolates were first molecularly analysed by means of randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). After strain differentiation (124 profiles), LAB were genetically identified at species level. The most frequently isolated LAB were lactococci, enterococci and streptococci. Lactobacilli, leuconostocs and pediococci were found at low levels. All strains …
Guanosine 5′-diphosphate 3′-diphosphate (ppGpp) as a negative modulator of polynucleotide phosphorylase activity in a ‘rare’ actinomycete
2010
With the beginning of the idiophase the highly phosphorylated guanylic nucleotides guanosine 5'-diphosphate 3'-diphosphate (ppGpp) and guanosine 5'-triphosphate 3'-diphosphate (pppGpp), collectively referred to as (p)ppGpp, activate stress survival adaptation programmes and trigger secondary metabolism in actinomycetes. The major target of (p)ppGpp is the RNA polymerase, where it binds altering the enzyme activity. In this study analysis of the polynucleotide phosphorylase (PNPase)-encoding gene pnp mRNA, in Nonomuraea sp. ATCC 39727 wild-type, constitutively stringent and relaxed strains, led us to hypothesize that in actinomycetes (p)ppGpp may modulate gene expression at the level of RNA …
Staphylococcus prevails in the skin microbiota of long-term immunodeficient mice
2012
Summary Host-commensal relationships in the skin are a complex system governed by variables related to the host, the bacteria and the environment. A disruption of this system may lead to new steady states, which, in turn, may lead to disease. We have studied one such disruption by characterizing the skin micro- biota in healthy and immunodepressed (ID) mice. A detailed anatomopathological study failed to reveal any difference between the skin of healthy and ID mice. We sequenced the 16S rDNA V1-V2 gene region to saturation in 10 healthy and 10 ID 8 week- old mice, and found than all of the healthy and two of the ID mice had bacterial communities that were similar in composition to that of h…
A method for taxonomic determination ofCandida albicans with DNA probes
1993
Determination of Candida species represents an important problem derived from the clinical implications of the species belonging to this genus. DNA probes have already been used for the epidemiology of Candida albicans, as well as for taxonomic analysis of Candida and other genera, although these probes are based on non-species-specific DNA sequences. In this work we carried out a 48-h assay, allowing the identification of C. albicans from clinical isolates, using DNA probes based on C. albicans LEU2 and URA3 genes. Another probe related to C. albicans SEC18 gene was shown not to be C. albicans specific.
Bacteria and Complement — A Historical Review
1985
In the second half of the nineteenth century, shortly after it became clear from the work of Louis Pasteur (1822–1895) and Robert Koch (1843–1910) that microorganisms cause infectious diseases, extensive studies were untertaken to elucidate the mechanisms of protection from and resistance to infections. This early history of the investigation of immunity is characterized by the dispute between two opposing schools, the protagonists of the “cellular” and the “humoral” theories. Eli Metchnikoff (1845–1919) was the first to recognize the general significance of the phenomenon of phagocytosis in animal tissues. In 1883, he published his first papers in the presentation of the theory of phagocyt…
Biosynthesis of the Collagen-like C1q Molecule and its Receptor Functions for Fc and Polyanionic Molecules on Macrophages
1983
At the beginning of the nineteenth century, knowledge of immunity was limited to a few practical methods based on empirical observations, e.g., the observation by Jenner in 1798 that inoculation with cowpox material induced an immunity to smallpox. The discoveries by Louis Pasteur and Robert Koch that microorganisms caused fermentations and were responsible for a number of infectious diseases, greatly advanced the concepts of susceptibility and immunity in a limited number of diseases. In the late nineteenth century, the complement system was discovered by Fodor(1887), Nuttall(1888), and Buchner (1889a, b) through studying the bactericidal action of blood serum. It was recognized that killi…
Survival in the soil of the ectomycorrhizal fungus Laccaria bicolor and the effects of a mycorrhiza helper Pseudomonas fluorescens
2001
In disinfected forest nursery soils, inoculating Douglas fir (Pseudotsuga menziesii) seedlings with the ectomycorrhizal fungal strain Laccaria bicolor S238N significantly increases tree growth after outplantating. However, the success of the inoculation depends on survival of the fungal inoculum in the soil during the pre-symbiotic life of the fungus. We followed the survival of L. bicolor S238N in autoclaved nursery soil in the glasshouse, and under gnotobiotic conditions in autoclaved or γ-irradiated nursery soil. We also studied the effect of the mycorrhiza helper bacterium Pseudomonas fluorescens BBc6R8, which promotes the Douglas fir-L. bicolor S238N symbiosis, on fungal viability. In …
Supression of Botrytis cinerea causing grey mould disease of grape vine (Vitis vinifera) and its pectinolytic activities by a soil bacterium
1997
Abstract Botrytis cinerea was found to be pathogenic to grapevine, producing characteristic grey mould symptoms within 7 days of inoculation into vitroplants. An endospore forming bacterial strain (GI 070), Bacillus circulans, was found to be antagonist against this disease causing fungus. Under laboratory conditions the bacterial culture or its filtrate brings about complete suppression of the fungus in Petri-dishes and the grey mould symptoms on grapevine vitroplants. Pectinolytic activities (Polygalacaturonase, Pectin lyases) of Botrytis cinerea were also influenced by these bacteria. Details of the fungal parasite, its biological control and its pectinolytic activities are discussed in …
TEM observations on symbionts ofJoenia annectens(Flagellata Hypermastigida)
2001
Transmission electron microscopy was used to evaluate the ultrastructural morphology of some other symbiotic prokaryotes of Joenia annectens, an intestinal flagellate of the termite Kalotermes flavicollis. Three morphotypes are predominant and recognizable from their morphological characteristics. One morphotype is represented by spirochaetes that are mainly external and cover the flagellate, helping its movement. Rod-shaped bacteria, which represent the second morphotype, are also attached to the surface among the spirochaetes. Rod-shaped bacteria and some spirochaetes may enter the cell surface of Joenia annectens as a consequence of phagocytosis, remaining enclosed in an envelope of plas…
Kinetics of citrate uptake in growing cells ofLeuconostocspp.
1996
Citrate uptake was studied in growing cells of Leuconostoc mesenteroides subsp. mesenteroides. A Michaelis-Menten pattern with the dianionic form of citrate as the limiting substrate has been proposed. It was validated for different fermentations varying the initial citrate concentrations and the pH medium. This latter did not modify the rate of the process which was clearly confirmed using experiments with resting cells. The model was used to compare the kinetics of citrate consumption between several strains of Leuconostoc mesenteroides subsp. mesenteroides, Leuconostoc mesenteroides subsp. cremoris and Leuconostoc lactis.