|
| ||
|
|
||
Cells G (cell + g)
Selected AbstractsTranscription dynamics of the functional tfdA gene during MCPA herbicide degradation by Cupriavidus necator AEO106 (pRO101) in agricultural soilENVIRONMENTAL MICROBIOLOGY, Issue 3 2008Mette Haubjerg Nicolaisen Summary A modified protocol for simultaneous extraction of RNA and DNA, followed by real-time polymerase chain reaction quantification, was used to investigate tfdA gene expression during in situ degradation of the herbicide MCPA (4-chloro-2-methylphenoxy-acetic acid) in soil. tfdA encodes an ,-ketoglutarate-dependent dioxygenase catalysing the first step in the degradation pathway of MCPA and 2,4-D (2,4-dichlorophenoxy-acetic acid). A linear recovery of tfdA mRNA over three orders of magnitude was shown, and the tfdA mRNA level was normalized using the tfdA mRNA/DNA ratio. The density of active cells required for tfdA mRNA detection was 105 cells g,1 soil. Natural soil microcosms inoculated with Cupriavidus necator (formerly Ralstonia eutropha) AEO106 (pRO101) cells were amended with four different MCPA concentrations (2, 20, 50 and 150 mg kg,1). Mineralization rates were estimated by quantification of 14CO2 emission from degradation of 14C-MCPA. tfdA mRNA was detected 1 h after amendment at all four concentrations. In soils amended with 2 and 20 mg kg,1, the mRNA/DNA ratio for tfdA demonstrated a sharp transient maximum of tfdA expression from no to full expression within 3 and 6 h respectively, followed by a decline and complete loss of expression after 19 and 43 h. A more complex pattern of tfdA expression was observed for the higher 50 and 150 mg kg,1 amendments; this coincided with growth of C. necator AEO106 (pRO101) in the system. Repeated amendment with MCPA after 2 weeks in the 20 mg kg,1 scenario revealed a sharp increase of tfdA mRNA, and absence of a mineralization lag phase. For all amendments, tfdA mRNA was detectable only during active mineralization, and thus revealed a direct correlation between tfdA mRNA presence and microbial degrader activity. The present study demonstrates that direct analysis of functional gene expression dynamics by quantification of mRNA can indeed be made in natural soil. [source] Chronic shedding of Campylobacter species in beef cattleJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2004G.D. Inglis Abstract Aims:, To determine the prevalence of chronic shedding of Campylobacter species by beef cattle, a longitudinal study of shedding patterns was conducted in a cohort of 60 beef steers over a 4-month period. Methods and Results:, Steers were maintained in a simulated feedlot setting but individually in pens to minimize transmission among animals. At each collection time, campylobacters in faeces were detected using conventional PCR. In addition, quantities of Campylobacter jejuni and C. lanienae in faeces were measured using real-time quantitative (RTQ) PCR. All of the steers tested shed Campylobacter species during the course of the study, and overall, 90% of the 299 samples tested were positive for Campylobacter DNA. The majority of the animals (86%) shed campylobacters at ,4 sample times. The most prevalent taxon detected in bovine faeces was C. lanienae (56% of samples) followed by C. jejuni (13%), C. hyointestinalis (8%), and C. fetus (2%). No C. coli was detected, and 13% of the faecal samples contained two or more of the above species. Seven (12%) and 34 (57%) animals shed C. jejuni and C. lanienae at ,3 sample times, respectively. For both C. lanienae and C. jejuni, a substantial number of cells were detected in faeces using RTQ-PCR; 27% of the samples positive for C. jejuni contained populations >104 cells g,1 (maximum of 5 × 105 cells g,1), and 44% of samples positive for C. lanienae possessed populations >106 cells g,1 (maximum of 4 × 108 cells g,1). A significant correlation was observed between shedding of C. lanienae and the severity of liver abscesses. In 27% of the samples, an amplicon was obtained for genus-specific but not for the species-specific primers. Sequencing of the partial 16S rRNA gene suggested the presence of at least two undescribed Campylobacter species but this has yet to be confirmed. Conclusions:, A high percentage of feedlot cattle shed large quantities of Campylobacter species in their faeces over a protracted period of time (ca 112 days). Significance and Impact of the Study:, This is the first study of longitudinal shedding patterns of campylobacters in beef cattle using PCR-detection methods. In addition, this is the first use of RTQ-PCR to directly quantify C. jejuni or C. lanienae in faeces. The results of the study show that a large number of cattle (>85%) chronically shed campylobacters in feedlots. [source] Response of methanogen populations to organic load increase during anaerobic digestion of olive mill wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2006Aurora Rizzi Abstract Process performances of an upflow anaerobic filter treating olive mill wastewater and the response of methanogenic Archaea to increasing volumetric organic load (VOL) were studied. At a VOL of 15 g chemical oxygen demand (COD) L,1 day,1, 90% of the influent COD was removed. Following a VOL increase from 6 to 15 g COD L,1 day,1, the polymerase chain reaction (PCR) titre of hydrogenotrophic Methanobacterium, determined by magnetic capture of the target DNA and group-specific PCR based on the 16S rRNA gene, decreased from 1011 to 108 cells g,1 sludge, while that of Methanomicrobiaceae and relatives increased from 104 to 106 cells g,1 sludge. Methanosaeta -like acetoclastic methanogens were less affected by VOL variation and dominated at high VOL with a 16S rRNA gene PCR titre of 109 cells g,1 sludge. Single-strand conformation polymorphism analysis of the PCR-amplified archaeal 16S rRNA gene showed a stable band pattern, indicating that VOL variation affected the methanogen PCR titre but not the archaeal community structure. Copyright © 2006 Society of Chemical Industry [source] Use of a probiotic to control lactococcosis and streptococcosis in rainbow trout, Oncorhynchus mykiss (Walbaum)JOURNAL OF FISH DISEASES, Issue 12 2005J Brunt Abstract From a comparison of 125 bacterial isolates recovered from the digestive tract of rainbow trout, Oncorhynchus mykiss, and carp, Cyprinus sp., a culture was obtained which was effective at preventing clinical disease caused by Lactococcus garvieae and Streptococcus iniae when used as a feed additive. The culture, Aeromonas sobria GC2, was incorporated into the feed and fed to rainbow trout (average weight = 20 g) for 14 days at a dose equivalent to 5 × 107 cells g,1 of feed. Whereas the untreated controls experienced losses of 75,100% when challenged intraperitoneally with L. garvieae and S. iniae, the probiotic-treated groups remained healthy with total mortalities of only 0,6%. Formalized and sonicated preparations of GC2 and cell-free supernatant fared less well. The mode of action reflected stimulation of innate immunity, namely an increased number of leucocytes and enhanced phagocytic and respiratory burst activity. [source] | ||||||||||