Comparison of disc diffusion and epsilometer (E-test) testing techniques to determine antimicrobial susceptibiliy of Campylobacter isolates of food and human clinical origin

The antibiotic resistance profiles of 75 Campylobacter isolates of food and human clinical origin was determined by two agar diffusion susceptibility methods; disc diffusion and epsilometer-test (E-test). The most common therapeutic antimicrobials, erythromycin, ciprofloxacin and tetracycline were studied, along with chloramphenicol, ampicillin and naladixic acid. The resistance observed for each antimicrobial, as determined by both of methods, were statistically compared using Fisher two-tailed analysis.Of the six antimicrobials studied only two were shown to have statistically different patterns when resistance was compared by disc diffusion and E-test. The percentage of isolates resistant to clinically relevant antimicrobials using both techniques ranged from 6.6 to 21.3% for erythromycin, 25.3–26.6% for tetracycline and 33.3–36.0% for ciprofloxacin. The prevalence of multi-drug resistant (MDR) campylobacters (isolates resistant to 2 or more antimicrobials) for both disc diffusion and E-test was 44%. It can be concluded that, for four of the six antimicrobials assessed, antimicrobial resistance prevalences could be equally determined by either of the methods studied.     

Reproductive evaluation of elephants culled in Kruger National Park, South Africa between 1975 and 1995

To reduce elephant densities and preserve biological diversity, 14,629 elephants were culled from Kruger National Park, South Africa (1967–1999). Data were catalogued between 1975 and 1996 on 2737 male and female elephants, including pregnancy and lactational status for 1620 females (≥5 years of age) and, uterine and/or ovarian characteristics for 1279. This study used these data to investigate the effects of age and precipitation on reproduction. The youngest age of conception was 8 years (n = 6) and by 12 years of age all females were sexually mature. From the age of 14 years, the percentage of reproductively active females (pregnant and/or lactating) was >90%; however, this percentage declined when females reached 50 years of age. Overall, one-tenth of females were nonreproductive (not pregnant or lactating) at any given time, mostly in the youngest (<15 years) and oldest (>50 years) age classes. Eighteen (3.3%) of the nonpregnant females had reproductive tract pathologies, including endometrial, uterine or ovarian cysts. There was a seasonal distribution of mating activity that correlated with the rainy season. As has been demonstrated in other populations of free-ranging African elephants, most of the females in Kruger National Park were reproductively active; however, age and climate affected reproductive activity.     

Identifying the neural circuitry of alcohol craving and relapse vulnerability

With no further intervention, relapse rates in detoxified alcoholics are high and usually exceed 80% of all detoxified patients. It has been suggested that stress and exposure to priming doses of alcohol and to alcohol-associated stimuli (cues) contribute to the relapse risk after detoxification. This article focuses on neuronal correlates of cue responses in detoxified alcoholics. Current brain imaging studies indicate that dysfunction of dopaminergic, glutamatergic and opioidergic neurotransmission in the brain reward system (ventral striatum including the nucleus accumbens) can be associated with alcohol craving and functional brain activation in neuronal systems that process attentional relevant stimuli, reward expectancy and experience. Increased functional brain activation elicited by such alcohol-associated cues predicted an increased relapse risk, whereas high brain activity elicited by affectively positive stimuli may represent a protective factor and was correlated with a decreased prospective relapse risk. These findings are discussed with respect to psychotherapeutic and pharmacological treatment options.     

Novel sulfur-oxidizing streamers thriving in perennial cold saline springs of the Canadian high Arctic

The perennial springs at Gypsum Hill (GH) and Colour Peak (CP), situated at nearly 80°N on Axel Heiberg Island in the Canadian high Arctic, are one of the few known examples of cold springs in thick permafrost on Earth. The springs emanate from deep saline aquifers and discharge cold anoxic brines rich in both sulfide and sulfate. Grey-coloured microbial streamers form during the winter months in snow-covered regions of the GH spring run-off channels (−1.3°C to 6.9°C, ∼7.5% NaCl, 0–20 p.p.m. dissolved sulfide, 1 p.p.m. dissolved oxygen) but disappear during the Arctic summer. Culture- and molecular-based analyses of the 16S rRNA gene (FISH, DGGE and clone libraries) indicated that the streamers were uniquely dominated by chemolithoautotrophic sulfur-oxidizing Thiomicrospira species . The streamers oxidized both sulfide and thiosulfate and fixed CO₂ under in situ conditions and a Thiomicrospira strain isolated from the streamers also actively oxidized sulfide and thiosulfate and fixed CO₂ under cold, saline conditions. Overall, the snow-covered spring channels appear to represent a unique polar saline microhabitat that protects and allows Thiomicrospira streamers to form and flourish via chemolithoautrophic, phototrophic-independent metabolism in a high Arctic winter environment characterized by air temperatures commonly below −40°C and with an annual average air temperature of −15°C. These results broaden our knowledge of the physical and chemical boundaries that define life on Earth and have astrobiological implications for the possibility of life existing under similar Martian conditions.     

Stable Isotope Probing Analysis of the Diversity and Activity of Methanotrophic Bacteria in Soils from the Canadian High Arctic

The melting of permafrost and its potential impact on CH₄ emissions are major concerns in the context of global warming. Methanotrophic bacteria have the capacity to mitigate CH₄ emissions from melting permafrost. Here, we used quantitative PCR (qPCR), stable isotope probing (SIP) of DNA, denaturing gradient gel electrophoresis (DGGE) fingerprinting, and sequencing of the 16S rRNA and pmoA genes to study the activity and diversity of methanotrophic bacteria in active-layer soils from Ellesmere Island in the Canadian high Arctic. Results showed that most of the soils had the capacity to oxidize CH₄ at 4°C and at room temperature (RT), but the oxidation rates were greater at RT than at 4°C and were significantly enhanced by nutrient amendment. The DGGE banding patterns associated with active methanotrophic bacterial populations were also different depending on the temperature of incubation and the addition of nutrients. Sequencing of the 16S rRNA and pmoA genes indicated a low diversity of the active methanotrophic bacteria, with all methanotroph 16S rRNA and pmoA gene sequences being related to type I methanotrophs from Methylobacter and Methylosarcina. The dominance of type I methanotrophs over type II methanotrophs in the native soil samples was confirmed by qPCR of the 16S rRNA gene with primers specific for these two groups of bacteria. The 16S rRNA and pmoA gene sequences related to those of Methylobacter tundripaludum were found in all soils, regardless of the incubation conditions, and they might therefore play a role in CH₄ degradation in situ. This work is providing new information supporting the potential importance of Methylobacter spp. in Arctic soils found in previous studies and contributes to the limited body of knowledge on methanotrophic activity and diversity in this extreme environment.Permafrost regions occupy approximately 22% of the exposed land area of the Northern Hemisphere (63). In the past 100 years, the average temperatures in the arctic regions have increased at almost twice the average global rate (25). The melting of permafrost is one of the most important impacts of global warming on these high-latitude environments, and theoretical modeling suggests that as much as 90% of the permafrost could thaw by the end of the 21st century (29). While it has been generally reported that 15% of the total soil organic carbon is stocked in permafrost (42), a recent estimate indicates that it contains as much as 50% of the global belowground organic carbon pool (53). Carbon stocked in permafrost is now regarded as one of the most important carbon-climate feedbacks because of the size of the carbon pool and the intensity of climate change at high latitudes (46, 47). The presence of these large amounts of carbon in permafrost is raising serious concerns whether melting permafrost, and the resulting increase in microbial activity, might be a source of extensive emissions of the greenhouse gases carbon dioxide and methane (CH₄) to the atmosphere. The actual emissions of CH₄ from soils of high latitudes have been estimated to represent about 25% of the emissions from natural sources (19). Methane, which is 25 times more potent than carbon dioxide as a greenhouse gas (25), is produced by methanogenic archaea under anaerobic conditions. These microorganisms are known to inhabit permafrost environments (44, 49), and their capacity to produce methane at cold temperatures has been reported (20, 35, 44, 56). Their methanogenic activity is expected to increase as permafrost soil temperature increases (20). Moreover, large amounts of methane are stocked as methane hydrates in permafrost at an average depth of several hundred meters (33). Methane is also found in permafrost layers near the surface and could potentially be liberated to the atmosphere as permafrost melts (44).Methane can be oxidized in aerobic zones by aerobic methanotrophic bacteria or in anaerobic zones by anaerobic methanotrophic archaea (for a recent review, see reference 27). Anaerobic methane oxidizers were not covered in the context of this study, which focused exclusively on aerobic methanotrophs. These bacteria utilize methane as the sole carbon and energy source through the activity of the enzyme methane monooxygenase (MMO). Most known aerobic methanotrophs are divided into two major groups (type I and type II) based on phylogeny and carbon assimilation pathways (5). Type I methanotrophs, also known as Gammaproteobacteria methanotrophs (6) belong to the family Methylococcaceae within the Gammaproteobacteria subdivision, while type II methanotrophs (Alphaproteobacteria methanotrophs) belong to the family Methylocystaceae in the Alphaproteobacteria subdivision (5). Because of their capacity to oxidize methane, aerobic methanotrophs can significantly reduce methane emissions to the atmosphere and play an important role in the global methane cycle (12, 22). Methanotrophic activity has been observed in cold environments, and methanotrophs might contribute to the reduction of methane emissions from melting permafrost. Aerobic methanotrophic bacteria from cold environments have been reviewed in detail elsewhere (54).Most studies addressing methanotrophs from cold environments were conducted on soils from very few sites located in Northern Europe and Siberia (14, 30, 31, 40, 56-58), while methanotrophic bacterial populations in soils from the Canadian high Arctic remain mostly unexplored (41). In addition, most of these studies were conducted at low latitudes, and the pool of knowledge concerning the activity and diversity of methanotrophic bacterial populations in high Arctic soils is limited. The question being addressed in this study is whether there are active methanotrophs in the active-layer soil in the high Arctic. Therefore, the present work had two objectives: (i) to evaluate the methane oxidation capacity of three active-layer soils from the Canadian high Arctic under various incubation conditions and (ii) to identify and characterize the diversity of the active methanotrophs in these soils using stable isotope probing (SIP) of DNA (DNA-SIP) and sequencing of the 16S rRNA and pmoA genes. With this work, we identify for the first time active methanotrophs in high Arctic soils through the use of DNA-SIP.     

Cloning and expression of single chain antibody fragments in Escherichia coli and Pichia pastoris

The potential of recombinant antibody fragments is likely to be fulfilled only if they can be produced routinely at high concentrations. We have compared the ability of Escherichia coli and Pichia pastoris to produce functional recombinant single chain antibody (scAb) fragments. Two scAb fragments were expressed, an antihuman type V acid phosphatase (TRAP) and an anti-Pseudomonas aeruginosa lipoprotein I. We report here that, while expression from P. pastoris resulted in a significantly increased level of expression of the anti-TRAP scAb compared to E. coli, neither fragment was able to bind its target antigen as well as the bacterial product.     

Geographical variation in temporal and spatial vocalization patterns of male harbour seals in the mating season

In the aquatically mating harbour seal, Phoca vitulina, oestrous females show marked differences in spatial and temporal distribution between geographical areas. This suggests that the males' display behaviour may also vary between areas. We recorded male vocalizations in two areas, the Moray Firth and Orkney, U.K. In the Moray Firth, females haul out on a few intertidal sandbars and travel along predictable routes to forage at sea. In Orkney, female haul out sites are much less influenced by tidal availability and females are much more dispersed. In the Moray Firth, males vocalized only during a short mating season, from 1 July to 12 August. Vocalizations varied significantly with the tide, the peak at high tide clearly coinciding with the period when most females were in the water. In contrast, vocalizations in Orkney were significantly related to both tidal and diel patterns. We suggest that the timing of male vocalizations reflects differences in female availability between sites. In the inner Moray Firth, vocalizations were heard throughout the females' range, whereas vocalizations in Orkney were heard only in two discrete areas. However, at both sites the density of vocalizing males was highest in narrow channels and/or along predictable female travel routes. Therefore, males clearly adapt their temporal and spatial behaviour patterns to variations in female distribution and density. These results suggest that male mating strategies in aquatically mating pinnipeds are more variable than was previously envisaged. Copyright 1999 The Association for the Study of Animal Behaviour.