Internal and External Influences on Near-Surface Microbial Community Structure in the Vicinity of the Cape Verde Islands

Microbial community structure in the subtropical north-east Atlantic Ocean was compared between 2 years and variation attributed to environmental variables. Surface seawater communities were analysed by flow cytometry and fluorescence in situ hybridisation. Probes specific to Alphaproteobacteria, Cyanobacteria, Gammaproteobacteria and Bacteroidetes identified 67–100% of cells. Due to natural variation in the study region due to the occurrence of major currents and islands, data could not be pooled but were instead divided between distinct water masses. Community structure did not differ greatly around the Cape Verde Islands between sampling periods but varied substantially in the open ocean, suggesting different environmental perturbations favour specific bacterial groups. Wind speed varied significantly between years, with moderate to strong breeze in winter 2008 and gales in winter 2006 (8.9 ± 0.2 ms⁻¹ and 16.0 ± 0.4 ms⁻¹, respectively). Enhanced wind-driven turbulence was associated with domination by the SAR11 clade of Alphaproteobacteria, which were present at 2.4-fold in the abundance of Prochlorococcus (41.8 ± 1.6% cells, compared to 17.7 ± 7.1%). Conversely, the calmer conditions of 2008 seemed to favour Prochlorococcus (40.0 ± 1.2% cells). Prochlorococcus high-light adapted clade HLI were only numerous during wind-driven turbulence, whereas oligotrophic-adapted clade HLII dominated under calm conditions. Bacteroidetes were most prominent in turbulent conditions (9.5 ± 1.3% cells as opposed to 4.7 ± 0.3%), as were Synechococcus. In 2008, a considerable dust deposition event occurred in the region, which may have led to the substantial Gammaproteobacteria population (22.5 ± 4.0% cells compared to 4.6 ± 0.6% in 2006). Wind-driven turbulence may have a significant impact on microbial community structure in the surface ocean. Therefore, community change following dust storm events may be linked to associated wind in addition to dust-derived nutrients.     

Role of a Tetraethylammonium-Sensitive Component of Potassium Currents in High-Frequency Tonic Impulsation Generated by Rat Retinal Ganglion Cells

Using the voltage/current clamp technique in the whole-cell configuration, we studied the role of the highly tetraethylammonium (TEA) -sensitive component of integral potassium current in the generation of high-frequency tonic impulsation by rat retinal ganglion cells (RGCs). Application of 0.5 mM TEA led to a decrease in the frequency of evoked tonic impulsation by RGCs by 63% (from 55 ± 10 sec^–1 in the control to 26 ± 5 sec^–1 in the presence of the blocker; n = 11). In this case, the duration of single action potentials at the level of 50% their amplitude increased by 64% (from 1.1 ± 0.1 to 1.8 ± 0.1 msec; n = 11), the rate of repolarization decreased by 54% (from −101 ± 9 to −46 ± 5 mV/msec; n = 11), and the amplitude of afterhyperpolarization dropped by 62% (from −16 ± 2 to −6 ± 2 mV; n = 11). Upon the action of 0.5 mM TEA, the amplitude of the integral potassium current in RGCs decreased; the current component sensitive to the above blocker was equal to 0.41 ± 0.05 nA (n = 6), while the respective value in the control was 1.62 ± 0.14 nA (n = 12). Thus, a moderate (on average, by 25%) decrease in the amplitude of the above potassium current significantly influenced the characteristics of impulse activity generated by RGCs. The TEA-sensitive component of the current was similar to the Kv3.1/Kv3.2 potassium current described earlier. The obtained data are indicative of the key role of the highly TEA-sensitive component of the potassium current (passed probably via Kv3.1/Kv3 channels) in high-frequency tonic activity generated by RGCs.     

Pyrosequencing Reveals a Highly Diverse and Cultivar-Specific Bacterial Endophyte Community in Potato Roots

In this study, we examined the bacterial endophyte community of potato (Solanum tuberosum) cultivar/clones using two different molecular-based techniques (bacterial automated ribosomal intergenic spacer analysis (B-ARISA) and pyrosequencing). B-ARISA profiles revealed a significant difference in the endophytic community between cultivars (perMANOVA, p < 0.001), and canonical correspondence analysis showed a significant correlation between the community structure and plant biomass (p = 0.001). Pyrosequencing detected, on average, 477 ± 71 bacterial operational taxonomic units (OTUs, 97% genetic similarity) residing within the roots of each cultivar, with a Chao estimated total OTU richness of 1,265 ± 313. Across all cultivars, a total of 238 known genera from 15 phyla were identified. Interestingly, five of the ten most common genera (Rheinheimera, Dyadobacter, Devosia, Pedobacter, and Pseudoxanthomonas) have not, to our knowledge, been previously reported as endophytes of potato. Like the B-ARISA analysis, the endophytic communities differed between cultivar/clones (∫-libshuff, p < 0.001) and exhibited low similarities on both a presence/absence (0.145 ± 0.019) and abundance (0.420 ± 0.081) basis. Seventeen OTUs showed a strong positive (r > 0.600) or negative (r < −0.600) correlation with plant biomass, suggesting a possible link between plant production and endophyte abundance. This study represents one of the most comprehensive assessments of the bacterial endophytic communities to date, and similar analyses in other plant species, cultivars, or tissues could be utilized to further elucidate the potential contribution(s) of endophytic communities to plant physiology and production.     

RETRACTED ARTICLE: Archaeal <Emphasis Type="Italic">amoA</Emphasis> Genes Outnumber Bacterial <Emphasis Type="Italic">amoA</Emphasis> Genes in Municipal Wastewater Treatment Plants in Bangkok

The contribution of ammonia-oxidizing archaea (AOA) to nitrogen removal in wastewater treatment plants (WWTPs) remains unknown. This study investigated the abundance of archaeal (AOA) and bacterial (ammonia-oxidizing bacteria (AOB)) amoA genes in eight of Bangkok’s municipal WWTPs. AOA amoA genes (3.28 × 10⁷ ± 1.74 × 10⁷–2.23 × 10¹¹ ± 1.92 × 10¹¹ copies l⁻¹ sludge) outnumbered AOB amoA genes in most of the WWTPs even though the plants’ treatment processes, influent and effluent characteristics, removal efficiencies, and operation varied. An estimation of the ammonia-oxidizing activity of AOA and AOB suggests that AOA involved in autotrophic ammonia oxidation in the WWTPs. Statistical analysis shows that the numbers of AOA amoA genes correlated negatively to the ammonium levels in effluent wastewater, while no correlation was found between the AOA amoA gene numbers and the oxygen concentrations in aeration tanks. An analysis of the AOB sequences shows that AOB found in the WWTPs limited to only two AOB clusters which exhibit high or moderate affinity to ammonia. In contrast to AOB, AOA sequences of various clusters were retrieved, and they were previously recovered from a variety of environments, such as thermal and marine environments.     

Dynamics of Bacterial Communities in Cockles (<Emphasis Type="Italic">Cerastoderma edule</Emphasis>) with Respect to Trematode Parasite (<Emphasis Type="Italic">Bucephalus minimus</Emphasis>) Infestation

The bacterial communities associated with the cockle (Cerastoderma edule) were investigated at the individual level through a 10-month monitoring programme. Temporal changes and those changes associated with a common parasite of the cockle, Bucephalus minimus, were investigated by monthly sampling of individuals, selected based on their shell length (cohort monitoring). Cockle bacterial community abundance (CBCA) and diversity (CBCD) were estimated by epifluorescence microscopy counts and automated ribosomal intergenic spacer analysis, respectively. CBCA showed a temporal pattern peaking at 30 × 10⁶ cells per gram of cockle flesh and intervalval liquid in October and a significant 1.8-fold increase linked with B. minimus occurrence. CBCD was characterized by 112 ± 26 intergenic transcribed spacer (ITS) per individual and showed a relative homology between individuals (52 ± 6%, Jaccard similarity) in spite of more than 30% of rare ITS. Consistent with an undisturbed evolution of the condition index of the studied cohort individuals as an estimate of their physiological state, neither temporal nor parasite-induced change in CBCA has been related to marked changes in CBCD.     

Invasion by a Perennial Herb Increases Decomposition Rate and Alters Nutrient Availability in Warm Temperate Lowland Forest Remnants

We determined the impact of the invasive herb, Tradescantia fluminensis Vell., on litter decomposition and nutrient availability in a remnant of New Zealand lowland podocarp–broadleaf forest. Using litter bags, we found that litter beneath mats of Tradescantia decomposed at almost twice the rate of litter placed outside the mat. Values of k (decomposition quotient) were 9.44±0.42 yrs for litter placed beneath Tradescantia and 5.42±0.42 yrs for litter placed in native, non-Tradescantia plots. The impact of Tradescantia on decomposition was evident through the smaller forest floor mass in Tradescantia plots (2.65±1.05 t ha⁻¹) compared with non-Tradescantia plots (5.05±1.05 t ha⁻¹), despite similar quantities of annual leaf litterfall into Tradescantia plots (6.85±0.85 t ha⁻¹ yr⁻¹) and non-Tradescantia plots (7.45±1.05 t ha⁻¹ yr⁻¹). Moreover, there was increased plant nitrate available, as captured on resin bags, in Tradescantia plots (25.77 ± 8.32 cmol(−)/kg resin) compared with non-Tradescantia plots (9.55±3.72 cmol(−)/kg resin). Finally, the annual nutrient uptake by Tradescantia represented a large proportion of nutrients in litterfall (41% N, 61% P, 23% Ca, 46% Mg and 83% K), exceeded the nutrient content of the forest floor (except Ca), but was a small proportion of the topsoil nutrient pools. Taken together, our results show that Tradescantia increases litter decomposition and alters nutrient availability, effects that could influence the long-term viability of the majority of podocarp–broadleaf forest remnants affected with Tradescantia in New Zealand. These impacts are likely mostly due to Tradescantia's vegetation structure (i.e., tall, dense mats) and associated microclimate, compared with native ground covers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of bacterial community structure in bulk soil by in situ hybridization

In situ hybridization with rRNA-targeted, fluorescent (Cy3-labeled) oligonucleotide probes was used to analyze bacterial community structure in ethanol- or paraformaldehyde-fixed bulk soil after homogenization of soil samples in 0.1% pyrophosphate by mild ultrasonic treatment. In ethanol-fixed samples 37 ± 7%, and in paraformaldehyde 41 ± 8% of the 4′, 6-diamidino-2-phenylindole(DAPI)-stained cells were detected with the bacterial probe Eub338. The yield could not be increased by enzymatic and/or chemical pretreatments known to enhance the permeability of bacterial cells for probes. However, during storage in ethanol for 7 months, the detectability of bacteria increased in both ethanol- and paraformaldehyde-fixed samples to up to 47 ± 8% due to an increase in the detection yield of members of the α-subdivision of Proteobacteria from 2 ± 1% to 10 ± 3%. Approximately half of the bacteria detected by probe Eub338 could be affiliated to major phylogenetic groups such as the α-, β-, γ-, and δ-subdivisions of Proteobacteria, gram-positive bacteria with a high G+C DNA content, bacteria of the Cytophaga-Flavobacterium cluster of the CFB phylum, and the planctomycetes. The analysis revealed that bacteria of the α- and δ-subdivision of Proteobacteria and the planctomycetes were predominant. Here, members of the α-subdivision of Proteobacteria accounted for approximately 10 ± 3% of DAPI-stained cells, which corresponded to 44 ± 16 × 10⁸ cells (g soil, dry wt.)^–1, while members of the δ-subdivision of Proteobacteria made up 4 ± 2% of DAPI-stained cells [17 ± 9 × 10⁸ cells (g soil, dry wt.)^–1]. A large population of bacteria in bulk soil was represented by the planctomycetes, which accounted for 7 ± 3% of DAPI-stained cells [32 ± 12 × 10⁸ cells (g soil, dry wt.)^–1]. The detection of planctomycetes in soil confirms previous reports on the occurrence of planctomycetes in soil and indicates a yet unknown ecological significance of this group, which to date has never been isolated from terrestrial environments. Received: 29 March 1997 / Accepted: 28 May 1997     

A comparison of photolyase activity in three Australian tree frogs

Ultraviolet-B (UV-B) irradiation of DNA generates mutagenic photoproducts such as cyclobutane pyrimidine dimers (CPDs) which can affect the growth and development of amphibian embryos. Differential ability to repair UV-B-induced DNA damage may be␣responsible for differences in population stability between␣some amphibian species. Photoreactivation via the enzyme photolyase is a major mechanism used to remove CPDs from DNA. The aim of this study was to determine if photolyase activity differed in three sympatric Australian amphibian species, one of which has suffered marked population declines (Litoria aurea) and two whose populations do not appear to be in decline (L. dentata and L. peronii). The specific activity of photolyase was measured in each species and compared to the hatching success of their eggs under unfiltered summer sunlight. The mean specific activities of photolyase were 1.10 ± 0.18 × 10¹¹, 5.76 ± 1.01 × 10¹¹, and 2.66 ± 0.15 × 10¹¹ CPDs repaired per hour per microgram of egg protein extract, for L. aurea, L. dentata and L. peronii, respectively. When intrinsic differences in hatching success between species were controlled for, the relative percentage hatching success under unfiltered sunlight of L. aurea (77%) was lower than that of L.␣peronii (91%) and L. dentata (98%); however, these values did not differ significantly. L. aurea had the lowest photolyase activity of the three species and showed a non-significant trend of reduced hatching success under UV-B exposure. Received: 15 December 1997 / Accepted: 9 March 1998     

Isoprenaline increases the slopes of restitution trajectory in the conscious rabbit with ischemic heart failure

Roughly speaking, restitution is the dependence of recovery time of cardiac electrical activity on heart rate. Increased restitution slope is theorized to be predictive of sudden death after heart injury such as from coronary artery occlusion (ischemia). Adrenaline analogs are known to increase restitution slope in normal hearts, but their effects in failing hearts are unknown. Twenty-six rabbits underwent coronary ligation (n = 15) or sham surgery (n = 11) and implantation of a lead in the heart for recording electrocardiograms. Eight weeks later, unanesthetized rabbits were given 0.25–2.0 ml of 1 μmol/L isoprenaline intravenously, which increased heart rate. Heart rate was quantified by time between QRS peaks (RR) and heart activity duration by R to T peak time (QTp). Ligated rabbits (n = 6) had lower ejection fraction than sham rabbits (n = 7, p < 0.0001) indicative of heart failure, but similar baseline RR (269 ± 15 vs 292 ± 23 ms, p = 0.07), QTp (104 ± 17 vs 91 ± 9 ms, p = 0.1), and isoprenaline-induced minimum RR (204 ± 11 vs 208 ± 6 ms, p = 0.4). The trajectory of QTp vs TQ plots displayed hysteresis and regions of negative slope. The slope of the positive slope region was >1 in ligated rabbits (1.27 ± 0.66) and <1 in sham rabbits (0.35 ± 0.14, p = 0.004). The absolute value of the negative slope was greater in ligated rabbits (− 0.81 ± 0.52 vs − 0.35 ± 0.14, p = 0.04). Isoprenaline increased heart rate and slopes of restitution trajectory in failing hearts. The dynamics of restitution trajectory may hold clues for sudden death in heart failure patients.     

Energy gain and loss during lactation and postweaning in southern elephant seal pups (Mirounga leonina) at King George Island

Deuterium-labeled water was used to measure changes in the proximate body composition during the lactation period and after weaning in southern elephant seal pups at King George Island, South Shetland Islands, Antarctica. During the lactation period (23.0 ± 1.4 days) pups gained a mean of 4.9 ± 0.5 kg/day (n=7). Of the total mass gain (112 ± 8 kg), 38% was water, 48% was fat, and 11% was protein. This represented an increase in total body gross energy of 2437 ± 145 MJ. The proportion of body mass represented by fat was less than 2% at birth, increasing to 35 ± 2% at weaning. We followed the pups during a mean period of 36 ± 3 days after weaning. During this period, pups had a mean loss of 1.21 ± 0.10 kg/day (n=7) comprising 39% water, 48% fat, and 12% protein. The energy cost over this period was 952 ± 168 MJ, which represented, on average, 39% of the total energy gained during the suckling period. Accepted: 3 January 2000     

Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China

In this study the red alga, Gracilaria lemaneiformis, was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 3 weeks at the Marine Aquaculture Laboratory of the Institute of Oceanology, Chinese Academy of Sciences (IOCAS) in Qingdao, Shandong Province, North China. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus from scallop excretion were determined. The experiment included four treatments each with three replicates, and three scallop monoculture systems served as the control. Scallop density (407.9 ± 2.84 g m⁻³) remained the same in all treatments while seaweed density differed. The seaweed density was set at four levels (treatments 1, 2, 3, 4) with thallus wet weight of 69.3 ± 3.21, 139.1 ± 3.80, 263.5 ± 6.83, and 347.6 ± 6.30 g m⁻³, respectively. There were no significant differences in the initial nitrogen and phosphorus concentration between each treatment and the control group (ANOVA, p > 0.05). The results showed that at the end of the experiment, the nitrogen concentration in the control group and treatment 1 was significantly higher than in the other treatments. There was also a significant difference in phosphorus concentration between the control group and the IMTA treatments (ANOVA, p < 0.05). Growth rate, C and N content of the thallus, and mortality of scallop was different between the IMTA treatments. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus changed with different cultivation density and time. The maximum reduction efficiency of ammonium and phosphorus was 83.7% and 70.4%, respectively. The maximum uptake rate of ammonium and phosphorus was 6.3 and 3.3 μmol g⁻¹ DW h⁻¹. A bivalve/seaweed biomass ratio from 1:0.33 to 1:0.80 (treatments 2, 3, and 4) was preferable for efficient nutrient uptake and for maintaining lower nutrient levels. Results indicate that G. lemaneiformis can efficiently absorb the ammonium and phosphorus from scallop excretion and is a suitable candidate for IMTA.     

Space use and habitat preferences of the invasive American mink (<Emphasis Type="Italic">Mustela vison</Emphasis>) in a Mediterranean area

Space use, intra-territorial habitat preferences, and factors affecting both were studied in an invading population of American mink, Mustela vison, in two rivers of a Mediterranean region of Spain. Average linear home range was 1.19 ± 0.73 km (±SD) and core area was 0.21 ± 0.08 km for resident males (n = 10); while for females (n = 5) they were 0.54 ± 0.14 and 0.19 ± 0.11 km, respectively. Overlapping between the home ranges of residents was low. In no case their core areas overlapped. Home ranges were small in comparison to other study areas and in general the resident minks were territorial. Linear home range length was related to individual weight and to the river. Weight had a positive effect indicating a potential body condition effect, while river may be showing a habitat quality effect. Habitat preferences were positively affected by the abundance of helophytic vegetation and negatively by the presence of human activity. Helophytic vegetation offers both food and refuges, while human activity may represent a potential danger. Percentage of captures was higher inside the core areas and was slightly influenced positively by abundance of helophytic vegetation. All this information should be considered when designing and implementing measures to control the expansion of American minks. We recommend keeping going with the trapping sessions but, given the results obtained, reducing the distance between traps down to 200 m to maximize capturability (i.e., about doubling the trapping effort), and, when available, placing them near helophytic vegetation. In the absence of helophytic vegetation, traps should be located near any kind of vegetation providing coverage for mink and far from human activity.     

Change in ammonia-oxidizing microorganisms in enriched nitrifying activated sludge

In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal amoA genes (5.70 × 10⁶ ± 3.30 × 10⁵ copies mg sludge⁻¹) to bacterial amoA genes (8.60 × 10⁶ ± 7.64 × 10⁵ copies mg sludge⁻¹) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations: 2, 10, and 30 mM NH₄⁺–N (28, 140, and 420 mg N l⁻¹). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation, comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l⁻¹), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l⁻¹), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels.     

Moderate exercise leads to decreased expression of β1 and β2 integrins on leucocytes

 Intravascular adhesion of leucocytes plays a role in the pathogenesis of acute and chronic vascular disease. Regular aerobic exercise seems to protect against vascular disease. Since leucocyte adhesion is mediated by integrins, we tested the hypothesis that surface expression of the integrin adhesive receptors LFA-1 (cd11a/cd18), MAC-1 (cd11b/cd18), gp 150/95 (cd11c/cd18), and VLA-4 (cd29/cd49) is decreased by moderate endurance exercise. Surface expression of integrins was measured by FACS analysis in 19 healthy subjects (16 males, 3 females, 36.6 ± 8.7 years, 177.1 ± 7.5 cm, 70.3 ± 8.1 kg) before and after submaximal exercise (3 h run) using monoclonal antibodies against cd11a, cd11b, cd11c, cd18, cd29 and cd49. In addition, we compared resting integrin expression in this group with a group of sedentary subjects (19 males, 6 females, 29.3 ± 5.3 years). White blood cell count increased from 5300 ml^–1 to 9740 ml^–1 during exercise (P<0.001). Nevertheless, the expression (indicated by the mean log fluorescence) of cd11a (94 ± 24 vs. 78 ± 14) and cd18 (128 ± 31 vs. 102 ± 21) on lymphocytes and of cd11a (104 ± 25 vs. 85 ± 16), cd11c (497 ± 171 vs. 408 ± 126) cd29 (109 ± 16 vs. 89 ± 16), cd49 (69± 8 vs. 54 ± 11) on monocytes was decreased after exercise (all P<0.05). In contrast, integrin expression on granulocytes was not altered by exercise. Comparison of exercising and sedentary subjects showed a significantly decreased expression of integrins in exercising subjects. Our results demonstrate that moderate exercise leads to decreased expression of integrin receptors on leucocytes. This decreased expression of adhesion molecules may result in decreased adhesion and infiltration of leucocytes into the vessel wall. This phenomenon may play a role in the beneficial effect of moderate exercise in prevention of acute and chronic vascular disease. Accepted: 18 March 1997     

Recruitment of the amphidromous goby <Emphasis Type="Italic">Sicyopterus japonicus</Emphasis> to the estuary of the Ota River,Wakayama, Japan

Ecological aspects of recruitment in the amphidromous goby, Sicyopterus japonicus, were studied from larval collections made with a set net in the estuary of the Ota River, Wakayama, Japan. The abundance patterns of the 12,766 larvae collected from 18 April to 26 August 2006 showed several peaks during the recruitment season. Their body sizes at recruitment ranged from 23.5 to 30.0 mm standard length (mean ± SD, 26.3 ± 1.1 mm), 0.11 to 0.49 g body weight (0.22 ± 0.05 g), and 8 to 20 condition factor (11 ± 2). The standard length of the goby larvae tended to decrease with the season, while their body weight slightly increased and resulted in an increase in condition factor. The recruitment of larvae occurred mainly during the daytime. Otolith growth increment analysis of 30 larvae collected by a square lift net on 30 April 2005 revealed that the oceanic larval duration after downstream migration ranged from 173 to 253 days (208 ± 22) after hatching. A limited time of recruitment in early summer and a considerably long duration of oceanic life (about a half year) appeared to be unique characteristics of this Sicyopterus species that lives in a temperate region in comparison to other tropical species of the genus Sicyopterus that all have year-round recruitment.     

Effect of stress pretreatment on survival of probiotic bacteria in gastrointestinal tract simulator

The effect of stress pretreatment on survival of probiotic Lactobacillus acidophilus La-5, Lactobacillus rhamnosus GG, and Lactobacillus fermentum ME-3 cultures was investigated in the single bioreactor gastrointestinal tract simulator (GITS). The cultures were pregrown in pH-auxostat, subjected to temperature, acid, or bile stress treatment, fast frozen in liquid nitrogen (LN₂), and tested for survival in GITS. After LN₂ freezing the colony forming ability of L. rhamnosus GG and L. fermentum ME-3 nonstressed and stressed cells was well retained (average survival of 75.4 ± 18.3% and 88.0 ± 7.2%, respectively). L. acidophilus La-5 strain showed good survival of auxostat nonstressed cells after fast freezing (94.2 ± 15.0), however the survival of stress pretreated cells was considerably lower (30.8 ± 8.5%). All LN₂ frozen auxostat cultures survived well in the acid phase of the GIT simulation (survival 81 ± 21%); however, after the bile phase, the colony formation ability of L. acidophilus La-5, L. rhamnosus GG, and L. fermentum ME-3 decreased by approximately 1.4 ± 0.2, 3.8 ± 0.3, and 3.5 ± 1.2 logarithmic units, respectively. No statistically relevant positive effect of stress pretreatments on survival of LN₂ frozen L. acidophilus La-5, L. rhamnosus GG, and L. fermentum ME-3 in GITS was observed.     

An annual cycle of dimethylsulfoniopropionate-sulfur and leucine assimilating bacterioplankton in the coastal NW Mediterranean

The contribution of major phylogenetic groups to heterotrophic bacteria assimilating sulfur from dissolved dimethylsulfoniopropionate (DMSP) and assimilating leucine was analysed in surface seawaters from Blanes Bay (NW Mediterranean) over an annual study between March 2003 and April 2004. The percentage of bacteria assimilating DMSP-S showed a strong seasonal pattern, with a steady increase from winter (8 +/- 5%) to summer (23 +/- 3%). The same seasonal pattern was observed for the rate of DMSP-S assimilation. The annual average percentage of DMSP-S-assimilating bacteria (16 +/- 8%) was lower than the corresponding percentage of leucine-assimilating cells (35 +/- 16%), suggesting that not all bacteria synthesizing protein incorporated DMSP-S. Smaller differences between both percentages were recorded in summer. Members of the Alphaproteobacteria (Roseobacter and SAR11) and Gammaproteobacteria groups accounted for most of bacterial DMSP-S-assimilating cells over the year. All major bacterial groups showed an increase of the percentage of cells assimilating DMSP-S during summer, and contributed to the increase of the DMSP-S assimilation rate in this period. In these primarily P-limited waters, enrichment with P + DMSP resulted in a stimulation of bacterial heterotrophic production comparable to, or higher than, that with P + glucose in summer, while during the rest of the year P + glucose induced a stronger response. This suggested that DMSP was more important a S and C source for bacteria in the warm stratified season. Overall, our results suggest that DMSP-S assimilation is controlled by the contribution of DMSP to S (and C) sources rather than by the phylogenetic composition of the bacterioplankton.     

Home range,range overlap,and site fidelity of introduced Siberian chipmunks in a suburban French forest

Home range size, range overlap, and multiyear site fidelity were investigated for introduced Siberian chipmunks (Tamias sibiricus) in a French suburban forest from bimonthly trapping sessions for 4 years (2004–2007). Annual home range sizes (100% minimum convex polygon, ±SE) were estimated from 39 trapping histories of 28 different adult residents. Males (N = 13, 1.86 ± 0.32 ha) had a home range 2.5 times larger than females (N = 26, 0.71 ± 0.08 ha); a male home range included significantly more trapping centers (arithmetic mean of capture locations) of females (5.5 ± 0.7) than of males (2.3 ± 0.5). Chipmunks exhibited strong multiyear site fidelity: mean distance between annual trapping centers of individuals trapped over two successive years was small (N = 82, 26 ± 2 m) compared to the largest home range length (ranging from 36 to 281 m); overlap between annual home range sizes of residents was 84 ± 5% (N = 11). These results improve our understanding of the space occupation of this unknown species in a novel environment.     

Relationships between bacterioplankton, chl a and temperature in Antarctic surface waters in summer

Spatial variations of bacterio- and phytoplankton were studied in order to compare their relationship in open-sea and coastal areas. Sampling was done quasi-synoptically south of the Antarctic Convergence in the Lazarev Sea and in the eastern part of the Weddell Sea during austral mid-summer. Thymidine incorporation rate was on average 1.10 nmol/m³ per hour in the open sea and 4.04  nmol/m³ per hour in the coastal area, bacterial abundance was 4.44 × 10¹¹ and 6.11 × 10¹¹ cells/m³ and chlorophyll a (chl a) was 0.43 and 2.42 mg/m³, respectively. Thymidine incorporation rate and chl a correlated positively in both the open-sea and coastal samples. In the coastal area bacterial numbers also correlated positively with chl a. The scale of spatial resolution was not important for detecting empirical relationships between phytoplankton and bacterioplankton parameters. In the coastal area, the low bacterial biomass in relation to chl a concentration compared to other oceans, indicates that generalised relationships between these parameters are not valid in Antarctic coastal waters. Grazing could not explain the discrepancy. The results suggest a strong coupling between phytoplankton and bacterioplankton. In addition, the results suggest that the bacterial assemblage in the coastal area was psychrophilic and well adapted to the prevailing low temperatures. Received: 18 October 1996 / Accepted: 8 December 1996