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Various Culture Conditions (various + culture_condition)
Selected AbstractsEffect of culture conditions on lactic acid production of Tetragenococcus speciesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2004T. Kobayashi Abstract Aims:, To investigate the effects of the salt concentration, incubation temperature and initial pH of the medium on the fermentative ability of the halophilic lactic acid bacteria, Tetragenococcus muriaticus and T. halophilus. Method and Results:, The growth, lactic acid production and pH reduction ability of five strains of T. muriaticus and T. halophilus in MRS broth medium under various culture conditions such as salt concentration (3, 7, 15 and 23% NaCl), temperature (20, 30 and 40°C), and initial medium pH (5·8, 6·5 and 7·5) were investigated. Those of T. halophilus were seriously affected by a high salinity (23% NaCl); in contrast, those of T. muriaticus were affected by a low initial pH (5·8). Conclusions:, The results indicate that high saline concentrations and low pH values have significant impact on the growth, lactic acid production and pH reduction ability of T. halophilus and T. muriaticus, respectively. Significance and Impact of the Study:, This study appears to be important in biopreservation during the manufacture of fermented food products. Both T. muriaticus and T. halophilus may support each other in reducing pH in hypersaline or low pH environment. To our knowledge, this is the first report on the fermentation ability of T. muriaticus. [source] Analysis of bacterial lipodepsipeptides by matrix-assisted laser desorption/ionisation time-of-flight and high-performance liquid chromatography with electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2001Simona Maria Monti Strains of certain plant pathogenic bacteria, in particular several pathovars of Pseudomonas syringae, are known to produce cyclic lipodepsipeptides (LDPs) endowed with peculiar structural features and noticeable biological activities. In this study, a mass spectrometry procedure is proposed for screening LDP-producing bacterial strains and for identifying and assessing individual LDPs. After matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) screening of thirteen P. syringae strains for LDP production, the extracts from culture filtrates of eight positive strains were subjected to electrospray mass spectrometry for the identification of LDPs. Five strains were found to produce two forms of syringomycins (SR-E and SR-G) and two forms of syringopeptin 25 (SP25A and SP25B); two strains produced SR-E, SR-G and a new form of SP22; one strain produced syringotoxin (ST) and syringostatin A (SS-A) in addition to SP25A and SP25B. The yield in culture of two major LPDs: SR-G (3.2,13.8,mg L,1) and SP25A (41.6,231.5,mg L,1) was assessed by and high-performance liquid chromatography with electrospray mass spectrometry (HPLC/ESI-MS) in both scan and single ion monitoring (SIM) modes. Results of this investigation showed that the mass spectrometry protocol developed here is a precise and reliable method for screening bacterial strains for LDP production and for assessing the amount of each metabolite under various culture conditions. This could be of practical value in view of potential applications, e.g. biocontrol of post-harvest fungal diseases. Copyright © 2001 John Wiley & Sons, Ltd. [source] Visualization of Surface-specific Antigens in Various Strains of Enterotoxigenic E. coliANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005S. Lüdi Proteinaceous surface antigens of enterotoxigenic E. coli (ETEC) appear as pili, and are important virulence factors as they allow bacteria to attach to the small intestinal mucosa. Surface antigens are classified as colonization factor antigens (CFA) and coli surface antigens (CS). Known groups include CFA/I, CFA/II (consisting of CS1, CS2 and CS3), CA/III and CFA/IV (consisting of CS4, CS5 and CS6). The goal of the present study was to examine the morphology of pili by transmission electron microscopy (TEM) and to localize specific surface antigens by immunolabelling. Using different strains of E. coli grown under various culture conditions, pili were visualized by negative staining and corresponding surface antigens were demonstrated by immunogold-labelling using both polyclonal and monoclonal antibodies. Expression of pili was dependent on culture conditions and sample handling. In contrast to CFA/I and CS3, CS6 pili were not detectable after negative staining. Selected antibodies, however, allowed surface antigens to be demonstrated unequivocally. These results will be of value in investigating the expression of colonizing factors in genetically modified bacterial strains. [source] Physiological Improvement to Enhance Escherichia coli Cell-Surface Display via Reducing Extracytoplasmic StressBIOTECHNOLOGY PROGRESS, Issue 2 2008Niju Narayanan Cell physiology was impaired when enhanced yellow fluorescence protein (EYFP) was displayed on the Escherichia coli cell surface, resulting in growth arrest and poor display performance. Coexpression of Skp, a periplasmic chaperone known to interact with several outer membrane proteins for their transport and insertion in the outer membrane, was demonstrated to be effective to restore cell physiology. When Skp was coexpressed with EYFP display, host cells became less sensitive to ethylenediaminetetraacetic acid and sodium dodecyl sulfate, implying that cell physiology was improved. Most importantly, the display performance was highly enhanced as a result of the increased specific fluorescence intensity without growth arrest. The results of transmission electron microscopy indicate that the density of surface-displayed EYFP was highly increased upon Skp coexpression. Cells with EYFP display experienced extracytoplasmic stress, as reflected by the induced promoter activities of three stress-responsive genes, degP, cpxP, and rpoH. The extracytoplasmic stress reflected by the degP promoter activity appears to be consistent with the cell physiology observed phenotypically under various culture conditions for cell-surface display. Therefore, the PdegP:: lacZ allele was proposed to be a suitable "sensor" for monitoring the extracytoplasmic stress and cell physiology during the course of E. coli cell-surface display. [source] Mueller,Hinton agar is superior to PDM blood agar for detection of methicillin-resistant Staphylococcus aureusCLINICAL MICROBIOLOGY AND INFECTION, Issue 1 2003T. Monsen The aim of this study was to compare the expression of oxacillin resistance in methicillin-resistant Staphylococcus aureus (MRSA) on Paper Disc Method agar supplemented with 5% defibrinated blood (PDM blood agar) and Mueller,Hinton agar supplemented with 2% NaCl (MH NaCl agar) using different susceptibility tests. Fifty mecA- containing isolates of S. aureus, exhibiting 46 different pulsed-field gel electrophoresis patterns, were comparatively tested using the E test, the single disk diffusion test, and the multipoint inoculation technique, under various culture conditions. The E test incubated at 35 °C for 24 h (breakpoint of resistance ,2.0 mg/L) detected 94% of the isolates on MH NaCl agar, compared with 28% for PDM blood agar (P < 0.05). The disk diffusion test (breakpoint ,,10 mm in diameter) under these incubation conditions detected resistance in 100% of the isolates on MH NaCl agar and in 80% of the isolates on PDM blood agar (P < 0.05). The multipoint technique (breakpoint ,1 mg/L), applied at 35 °C for 24 h, detected 100% on MH NaCl agar and 46% on PDM blood agar (P < 0.05). Irrespective of the method of susceptibility testing evaluated, MH NaCl agar was superior to PDM blood agar for the detection of oxacillin resistance in mecA -containing S. aureus. [source] | ||||||||||