Superoxide dismutase is upregulated in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> following protoporphyrin-mediated photodynamic inactivation and does not directly influence the response to photodynamic treatment

Background  

Staphylococcus aureus, a major human pathogen causes a wide range of disease syndromes. The most dangerous are methicillin-resistant S. aureus (MRSA) strains, resistant not only to all β-lactam antibiotics but also to other antimicrobials. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance can not be developed easily. Among others, photodynamic inactivation (PDI) of S. aureus is a promising option. Photodynamic inactivation is based on a concept that a non toxic chemical, called a photosensitizer upon excitation with light of an appropriate wavelength is activated. As a consequence singlet oxygen and other reactive oxygen species (e.g. superoxide anion) are produced, which are responsible for the cytotoxic effect towards bacterial cells. As strain-dependence in photodynamic inactivation of S. aureus was observed, determination of the molecular marker(s) underlying the mechanism of the bacterial response to PDI treatment would be of great clinical importance. We examined the role of superoxide dismutases (Sod) in photodynamic inactivation of S. aureus as enzymes responsible for oxidative stress resistance.     

Synergistic effect of hypocrellin B and curcumin on photodynamic inactivation of Staphylococcus aureus

Antimicrobial photodynamic inactivation (aPDI) serves as a new approach to control the growth of foodborne bacteria. It remains elusive if the photodynamic efficacy of hypocrellin B (HB) can be potentiated by joint action with curcumin. In this study, we measured the survival rate of Staphylococcus aureus strains under the varying photodynamic conditions. According to our data, a maximum of 5–6 log₁₀ decrease of bacterial survival can be achieved under the tested conditions (500 nM, 9 J cm^‒2). Regarding the bactericidal mechanisms, HB-based aPDI disrupted the membrane integrity of staphylococcal cells, probably owing to the stimulated reactive oxygen species (ROS). In addition, aPDI disrupted the enzymatic activities of bacterial antioxidant proteins and caused the leakage of multiple intracellular substances. The HB-mediated photodynamic efficacy was potentiated by the addition of curcumin with a sublethal dose. This dual-photon synergy arose from unique aPDI conditions (100 nM each and 9 J cm^‒2). The synergistic action might be accounted for by the increased type I/type II ratio of ROS, as evidenced by the effect of different quenchers. Finally, the joint use of photosensitizers reduced the microbial contamination of the tested apple while maintaining its quality. In summary, photodynamic inactivation based on dual photons showed synergistic activity in controlling the growth of Staphylococcal aureus, which provided a novel approach to maintain food safety.     

Frequency of Antibiotic Resistance in a Swine Facility 2.5 Years After a Ban on Antibiotics

The addition of antibiotics to livestock feed has contributed to the selection of antibiotic-resistant bacteria in concentrated animal feeding operations and agricultural ecosystems. The objective of this study was to assess the occurrence of resistance to chlortetracycline and tylosin among bacterial populations at the Swine Complex of McGill University (Province of Quebec, Canada) in the absence of antibiotic administration to pigs for 2.5 years prior to the beginning of this study. Feces from ten pigs born from the same sow and provided feed without antibiotic were sampled during suckling (n = 6 for enumerations, n = 10 for PCR), weanling (n = 10 both for PCR and enumerations), growing (n = 10 both for PCR and enumerations), and finishing (n = 10 both for PCR and enumerations). The percentage of chlortetracycline-resistant anaerobic bacterial populations (Tet^R) was higher than that of tylosin-resistant anaerobic bacterial populations (Tyl^R) at weanling, growing, and finishing. Prior to the transportation of animals to the slaughterhouse, resistant populations varied between 6.5 and 9.4 Log colony-forming units g humid feces⁻¹. In all pigs, tet(L), tet(O), and erm(B) were detected at suckling and weanling, whereas only tet(O) was detected at growing and finishing. The abundance of tet(O) was similar between males and females at weanling and growing and reached 5.1 × 10⁵ and 5.6 × 10⁵ copies of tet(O)/ng of total DNA in males and females, respectively, at finishing. Results showed high abundances and proportions of Tet^R and Tyl^R anaerobic bacterial populations, as well as the occurrence of tet and erm resistance genes within these populations despite the absence of antibiotic administration to pigs at this swine production facility since January 2007, i.e., 2.5 years prior to the beginning of this study. This work showed that the occurrence of bacterial resistance to chlortetracycline and tylosin is high at the Swine Complex of McGill University.     

Enumeration of bacteria from a Trichodesmium spp. bloom of the Eastern Arabian Sea: elucidation of their possible role in biogeochemistry

The carbon-flux via algal bloom events involves bacteria as an important mediator. The present study, carried out during the spring inter-monsoon month of April 2008 onboard CRV Sagar Manjusha-06 in the Eastern Arabian Sea, addresses the bloom-specific flow of carbon to bacteria via chromophoric dissolved organic matter (CDOM). Eleven stations monitored were located in the coastal, shelf and open-ocean areas off Ratnagiri (16°59′N, 73°17′E), Goa (15°30′N, 73°48′E) and Bhatkal (13°58′N, 74°33′E) coasts. Visible bloom of “saw-dust” color in the Ratnagiri shelf were microscopically examined and the presence of cyanobacteria Trichodesmium erythraeum and T. thieabautii with cell concentrations as high as 3.05 × 10⁶ trichomes L⁻¹ was recorded. Total bacterial counts (TBC) varied between 94.09 × 10⁸ cells L⁻¹ in the bloom to 1.34 × 10⁸ cells L⁻¹ in the non-bloom area. Chromophoric dissolved organic matter (CDOM) concentrations averaged 2.27 ± 3.02 m⁻¹ (absorption coefficient 325 nm) in the bloom to 0.28 ± 0.07 m⁻¹ in the non-bloom waters respectively. CDOM composition varied from a higher molecular size with lower aromaticity in the bloom to lower molecular size and increased aromaticity in the non-bloom areas respectively. Strong positive relationship of TBC with Chlorophyll a (R ² = 0.65, p < 0.01) and CDOM concentrations (R ² = 0.8373, p = 0.01) in the bloom area indicated hydrolysis and/or uptake of CDOM by bacteria. Absorption by mycosporine-like amino acid palythene (λ _max = 360 nm) was recorded in the filtrate of bloom. Morphotypes of Trichodesmium-associated bacteria revealed a higher frequency of Gram-positive rods. The role of bacteria in relation to changing CDOM nature and as a factor in affecting oxygen content of the water column is discussed in context of the Arabian Sea.     

Ecological Characterisation of the Colonic Microbiota in Arctic and Sub-Arctic Seals

Dominant colonic bacteria in wild hooded (n = 9), harbour (n = 1) and grey (n = 1) seals were identified using 16S rRNA gene clone libraries (313 clones), revealing 52.7% Bacteroidetes, 41.5% Firmicutes, 4.5% Proteobacteria and 1.0% Fusobacteria. Thirty (77%) of the 39 phylotypes identified were novel, showing <97% sequence similarity to their nearest cultivated relatives. Mean colonic bacterial cell density, determined by real-time PCR, was high (12.8 log₁₀ cells/g wet wt) for the hooded seals, while the number of methanogenic Archea was low (4.0 log₁₀ cells/g wet wt). The level of ampicillin (amp^r) and tetracycline-resistant (tet^r) isolates was investigated by cultivation. Aerobic amp^r isolates were only detected in colon contents from four hooded seals, whereas aerobic tet^r isolates were found in seven of the nine hooded seals. These data provide novel insight to the gut microbiota of Arctic and sub-Arctic seals living in the wild.     

Palm oil mill effluent (POME) cultured marine microalgae as supplementary diet for rotifer culture

Malaysia is the world’s leading producer of palm oil products that contribute US$ 7.5 billion in export revenues. Like any other agro-based industries, it generates waste that could be utilized as a source of organic nutrients for microalgae culture. Present investigation delves upon Isochrysis sp. culture in POME modified medium and its utilization as a supplement to Nanochloropsis sp. in rotifer cultures. The culture conditions were optimized using a 1 L photobioreactor (Temp: 23°C, illumination: 180 ∼ 200 μmol photons m⁻²s⁻¹, n = 6) and scaled up to 10 L outdoor system (Temp: 26–29°C, illumination: 50 ∼ 180 μmol photons m⁻²s⁻¹, n = 3). Algal growth rate in photobioreactor (μ = 0.0363 h⁻¹) was 55% higher compared to outdoor culture (μ = 0.0163 h⁻¹), but biomass production was 1.3 times higher in outdoor culture (Outdoor = 91.7 mg m⁻²d⁻¹; Photobioreactor = 69 mg m⁻²d⁻¹). Outdoor culture produced 18% higher lipid; while total fatty acids (FA) was not significantly affected by the change in culture systems as both cultures yield almost similar concentrations of fatty acids per gram of sample (photobioreactor = 119.17 mg g⁻¹; outdoor culture = 104.50 mg g⁻¹); however, outdoor cultured Isochrysis sp. had 26% more polyunsaturated fatty acids (PUFAs). Rotifers cultured in Isochrysis sp./ Nanochloropsis sp. (1:1, v/v) mixture gave similar growth rate as 100% Nanochoropsis sp. culture (μ = 0.40 d⁻¹), but had 45% higher counts of rotifers with eggs (t = 7, maximum). The Isochrysis sp. culture successfully lowered the nitrate (46%) and orthophosphate (83%) during outdoor culture.     

Neustonic versus epiphytic bacteria of eutrophic lake and their biodegradation ability on deltamethrin

This study evaluated biodegradation of the insecticide deltamethrin (1 μg l⁻¹) by pure cultures of neustonic (n = 25) and epiphytic (n = 25) bacteria and by mixed cultures (n = 1), which consisted of a mixture of 25 bacterial strains isolated from the surface microlayer (SM ≈ 250 μm) and epidermis of the Common Reed (Phragmites australis, (Cav.) Trin. ex Steud.) growing in the littoral zone of eutrophic lake Chełmżyńskie. Results indicate that neustonic and epiphytic bacteria are characterized by a similar average capacity to degrade deltamethrin. After a 15-day incubation, bacteria isolated from the surface microlayer reduced the initial concentration of deltamethrin by 60%, while the average effectiveness of the bacteria found on the Common Reed equaled 47%.     

Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater

It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH₄⁺–N g total suspended solids (TSS)⁻¹ day⁻¹, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria (AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia load. At the ammonia load of 0.3 ± 0.002 mg NH₄⁺–N g TSS⁻¹ day⁻¹, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass.     

Kinetics of styrene biodegradation by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. E-93486

The research into kinetics of styrene biodegradation by bacterial strain Pseudomonas sp. E-93486 coming from VTT Culture Collection (Finland) was presented in this work. Microbial growth tests in the presence of styrene as the sole carbon and energy source were performed both in batch and continuous cultures. Batch experiments were conducted for initial concentration of styrene in the liquid phase changed in the range of 5–90 g m⁻³. The Haldane model was found to be the best to fit the kinetic data, and the estimated constants of the equation were: μ _m = 0.1188 h⁻¹, K _S = 5.984 mg l⁻¹, and K _i = 156.6 mg l⁻¹. The yield coefficient mean value Y_\textxs^\textapp Y_{\text{xs}}^{\text{app}} for the batch culture was 0.72 g_{dry cells weight} (g_substrate)⁻¹. The experiments conducted in a chemostat at various dilution rates (D = 0.035–0.1 h⁻¹) made it possible to determine the value of the coefficient for maintenance metabolism m _d = 0.0165 h⁻¹ and the maximum yield coefficient value Y_\textxs^\textM = 0.913 Y_{\text{xs}}^{\text{M}} = 0.913 . Chemostat experiments confirmed the high value of yield coefficient Y_\textxs^\textapp Y_{\text{xs}}^{\text{app}} observed in the batch culture. The conducted experiments showed high activity of the examined strain in the styrene biodegradation process and a relatively low sensitivity to inhibition of its growth at higher concentrations of styrene in the solution. Such exceptional features of Pseudomonas sp. E-93486 make this bacterial strain the perfect candidate for technical applications.     

Liver damage and systemic inflammatory responses are exacerbated by the genetic deletion of CD39 in total hepatic ischemia

Liver ischemia reperfusion injury is associated with both local damage to the hepatic vasculature and systemic inflammatory responses. CD39 is the dominant vascular endothelial cell ectonucleotidase and rapidly hydrolyses both adenosine triphosphate (ATP) and adenosine diphosphate to adenosine monophosphate. These biochemical properties, in tandem with 5′-nucleotidases, generate adenosine and potentially illicit inflammatory vascular responses and thrombosis. We have evaluated the role of CD39 in total hepatic ischemia reperfusion injury (IRI). Wildtype mice, Cd39-hemizygous mice (+/−) and matched Cd39-null mice (−/−); (n = 25 per group) underwent 45 min of total warm ischemia with full inflow occlusion necessitating partial hepatectomy. Soluble nucleoside triphosphate diphosphohydrolase (NTPDases) or adenosine/amrinone were administered to wildtype (n = 6) and Cd39-null mice (n = 6) in order to study protective effects in vivo. Parameters of liver injury, systemic inflammation, hepatic ATP determinations by P³¹-NMR and parameters of lung injury were obtained. All wildtype mice survived up to 7 days with minimal biochemical disturbances and minor evidence for injury. In contrast, 64% of Cd39+/− and 84% of Cd39-null mice required euthanasia or died within 4 h post-reperfusion with liver damage and systemic inflammation associated with hypercytokinemia. Hepatic ATP depletion was pronounced in Cd39-null mice posthepatic IRI. Soluble NTPDase or adenosine administration protected Cd39-deficient mice from acute reperfusion injury. We conclude that CD39 is protective in hepatic IRI preventing local injury and systemic inflammation in an adenosine dependent manner. Our data indicate that vascular CD39 expression has an essential protective role in hepatic IRI.     

Phylogenetic and Physiological Diversity of Bacteria Isolated from Puruogangri Ice Core

The microbial abundance, the percentage of viable bacteria, and the diversity of bacterial isolates from different regions of a 83.45-m ice core from the Puruogangri glacier on the Tibetan Plateau (China) have been investigated. Small subunit 16S rRNA sequences and phylogenetic relationships have been studied for 108 bacterial isolates recovered under aerobic growth conditions from different regions of the ice core. The genomic fingerprints based on ERIC (enterobacterial repetitive intergenic consensus)-polymerase chain reaction and physiological heterogeneity of the closely evolutionary related bacterial strains isolated from different ice core depths were analyzed as well. The results showed that the total microbial cell, percentages of live cells, and the bacterial CFU ranged from 10⁴ to 10⁵ cell ml⁻¹ (Mean, 9.47 × 10⁴; SD, 5.7 × 10⁴, n = 20), 25–81%, and 0–760 cfu ml⁻¹, respectively. The majority of the isolates had 16S rRNA sequences similar to previously determined sequences, ranging from 92 to 99% identical to database sequences. Based on their 16S rRNA sequences, 42.6% of the isolates were high-G + C-content (HGC) gram-positive bacteria, 35.2% were low-G + C (LGC) gram-positive bacteria, 16.6% were Proteobacteria, and 5.6% were CFB group. There were clear differences in the depth distribution of the bacterial isolates. The isolates tested exhibited unique phenotypic properties and high genetic heterogeneity, which showed no clear correlation with depths of bacterial isolation. This layered distribution and high heterogeneity of bacterial isolates presumably reflect the diverse bacterial sources and the differences in bacteria inhabiting the glacier’s surface under different past climate conditions.     

Changes in Morphology and Elemental Composition of <Emphasis Type="Italic">Vibrio splendidus</Emphasis> Along a Gradient from Carbon-limited to Phosphate-limited Growth

We examined morphology, elemental composition (C, N, P), and orthophosphate-uptake efficiency in the marine heterotrophic bacterium Vibrio splendidus grown in continuous cultures. Eight chemostats were arranged along a gradient of increasing glucose concentrations in the reservoirs, shifting the limiting factor from glucose to phosphate. The content of carbon, nitrogen, and phosphorus was measured in individual cells by x-ray microanalysis using a transmission electron microscope (TEM). Cell volumes (V) were estimated from length and width measurements of unfixed, air-dried cells in TEM. There was a transition from coccoid cells in C-limited cultures toward rod-shaped cells in P-limited cultures. Cells in P-limited cultures with free glucose in the media were significantly larger than cells in glucose-depleted cultures (P < 0.0001). We found functional allometry between cellular C-, N-, and P content (in femtograms) and V (in cubic micrometers) in V. splendidus (C = 224 × V ^0.89, N = 52.5 × V ^0.80, P = 2 × V ^0.65); i.e., larger bacteria had less elemental C, N, and P per V than smaller cells, and also less P relative to C. Biomass-specific affinity for orthophosphate uptake in large P-limited V. splendidus approached theoretical maxima predicted for uptake limited by molecular diffusion toward the cells. Comparing these theoretical values to respective values for the smaller, coccoid, C-limited V. splendidus indicated, contrary to the traditional view, that large size did not represent a trade-off when competing for the non-C-limiting nutrients.     

Space use and territoriality of wolverines (<Emphasis Type="Italic">Gulo gulo</Emphasis>) in northern Scandinavia

Space use and territoriality influence population structure and dynamics and is therefore an important aspect in understanding the ecology of animals. We investigated spatial and temporal space use of wolverines (Gulo gulo) in northern Scandinavia. We estimated home ranges of 24 radio-marked individuals (17 females and seven males). Male home ranges (mean 669 km²; SE = 211) were significantly larger than female home ranges (mean 170 km²; Wilcoxon–Mann–Whitney; P = 0.001) and encompassed or included parts of up to five different females. Home range sizes of reproducing (170 km²; SE = 51) and barren (171 km²; SE = 63) adult females did not differ. Wolverines in Scandinavia exhibit intrasexual territoriality, with male home ranges totally exclusive and female home ranges either exclusive or with little home range overlap. Overlap between wolverine territories is most likely explained by intrasexual tolerance and kinship.     

Phosphate Addition and Plant Species Alters Microbial Community Structure in Acidic Upland Grassland Soil

Agricultural improvement (addition of fertilizers, liming) of seminatural acidic grasslands across Ireland and the UK has resulted in significant shifts in floristic composition, soil chemistry, and microbial community structure. Although several factors have been proposed as responsible for driving shifts in microbial communities, the exact causes of such changes are not well defined. Phosphate was added to grassland microcosms to investigate the effect on fungal and bacterial communities. Plant species typical of unimproved grasslands (Agrostis capillaris, Festuca ovina) and agriculturally improved grasslands (Lolium perenne) were grown, and phosphate was added 25 days after seed germination, with harvesting after a further 50 days. Phosphate addition significantly increased root biomass (p < 0.001) and shoot biomass (p < 0.05), soil pH (by 0.1 U), and microbial activity (by 5.33 mg triphenylformazan [TPF] g⁻¹ soil; p < 0.001). A slight decrease (by 0.257 mg biomass-C g⁻¹ soil; p < 0.05) in microbial biomass after phosphate addition was found. The presence of plant species significantly decreased soil pH (p < 0.05; by up to 0.2 U) and increased microbial activity (by up to 6.02 mg TPF g⁻¹ soil) but had no significant effect on microbial biomass. Microbial communities were profiled using automated ribosomal intergenic spacer analysis. Multidimensional scaling plots and canonical correspondence analysis revealed that phosphate addition and its interactions with upland grassland plant species resulted in considerable changes in the fungal and bacterial communities of upland soil. The fungal community structure was significantly affected by both phosphate (R = 0.948) and plant species (R = 0.857), and the bacterial community structure was also significantly affected by phosphate (R = 0.758) and plant species (R = 0.753). Differences in microbial community structure following P addition were also revealed by similarity percentage analysis. These data suggest that phosphate application may be an important contributor to microbial community structural change during agricultural management of upland grasslands.     

In Vitro Antibacterial Activity of 4-Phenyl-1-(2-phenyl-allyl)pyridinium bromide: A Novel Class of Pyridinium Based Antibacterial Compounds

The continuing increase in the incidence of multi drug resistant pathogenic bacteria and shortage of new antimicrobial agents are the prime driver in efforts to identify the novel antimicrobial classes. In vitro antibacterial activity of 4-phenyl-1-(2-phenylallyl) pyridinium bromide was tested against Gram positive Staphylococcus aureus, Streptococcus species, Bacillus subtilis, and Gram negative Klebsiella aerogenes and Escherichia coli using disk diffusion method. Among them S. aureus showed strong antibacterial activity (21.99 ± 0.03 mm) while E. coli showed very little activity (8.97 ± 0.06 mm) towards the compound. The MIC of 4-phenyl-1-(2-phenyl-allyl)-pyridinium bromide for 90% S. aureus was ≤20 μg/ml and was compared with phenoxymethylpenicillin, cloxacillin, erythromycin and vancomycin. When 4-phenyl-1-(2-phenyl-allyl)pyridinium bromide showed MIC at ≤20 μg/ml, all others showed MIC at ≤100 μg/ml. Strong antibacterial activity of 4-phenyl-1-(2-phenyl-allyl)pyridinium bromide against S. aureus indicates that there is a possibility to use it as an effective antibacterial agent.     

Stress-Induced Changes in Optical Properties,Pigment and Fatty Acid Content of <Emphasis Type="Italic">Nannochloropsis</Emphasis> sp.: Implications for Non-destructive Assay of Total Fatty Acids

In order to develop a practical approach for fast and non-destructive assay of total fatty acid (TFA) and pigments in the biomass of the marine microalga Nannochloropsis sp. changes in TFA, chlorophyll, and carotenoid contents were monitored in parallel with the cell suspension absorbance. The experiments were conducted with the cultures grown under normal (complete nutrient f/2 medium at 75 μmol PAR photons/(m² s)) or stressful (nitrogen-lacking media at 350 μmol PAR photons/(m² s)) conditions. The reliable measurement of the cell suspension absorbance using a spectrophotometer without integrating sphere was achieved by deposition of cells on glass–fiber filters in the chlorophyll content range of 3–13 mg/L. Under stressful conditions, a 30–50% decline in biomass and chlorophyll, retention of carotenoids and a build-up of TFA (15–45 % of dry weight) were recorded. Spectral regions sensitive to widely ranging changes in carotenoid-to-chlorophyll ratio and correlated changes of TFA content were revealed. Employing the tight inter-correlation of stress-induced changes in lipid metabolism and rearrangement of the pigment apparatus, the spectral indices were constructed for non-destructive assessment of carotenoid-to-chlorophyll ratio (range 0.3–0.6; root mean square error (RMSE) = 0.03; r ² = 0.93) as well as TFA content of Nannochloropsis sp. biomass (range 5.0–45%; RMSE = 3.23 %; r ² = 0.89) in the broad band 400–550 nm normalized to that in chlorophyll absorption band (centered at 678 nm). The findings are discussed in the context of real-time monitoring of the TFA accumulation by Nannochloropsis cultures under stressful conditions.     

Fermentation of mucin by bifidobacteria from rectal samples of humans and rectal and intestinal samples of animals

Bifidobacteria (246 strains in total) were isolated from rectal samples of infants and adult humans and animals, and from intestinal samples of calves. Twenty-five strains grew well on mucin: 20 from infants, two from adults, and three from goatlings. Poor or no growth on mucin was observed in 156 bifidobacterial strains of animal origin. The difference between human and animal isolates in ability to grow on mucin was significant at p < 0.001. Nine human strains with the best growth on mucin were identified as Bifidobacterium bifidum. These strains produced extracellular, membrane-bound, and intracellular mucinases with activities of 0.11, 0.53, and 0.09 μmol/min of reducing sugars per milligram of protein, respectively. Membrane-bound mucinases were active between pH 5 and 10. The optimum pH of extracellular mucinases was 6–7. Fermentation patterns in cultures grown on mucin and glucose differed. On mucin, the acetate-to-lactate ratio was higher than in cultures grown on glucose (p = 0.012). We showed that the bifidobacteria belong to the mucin-fermenting bacteria in humans, but their significance in mucin degradation in animals seems to be limited.     

Thermogenic responses to body cooling during fever induced by Staphylococcus aureus cell walls in rabbits

Hypothalamic temperature (T _hypo) and metabolic heat production (M) were measured in seven conscious rabbits injected intravenously with either saline or with Staphylococcus aureus, (8 · 10⁷ cell walls · kg⁻¹) while being subjected to a 3-h period of ramp-like total body cooling using a chronically implanted intravascular heat exchanger. In pyrogen-injected animals cooling started (1) at the time of injection or (2) 70 min after injection. In (1) the fall in T _hypo induced by heat extraction was similar (1.0 °C) in afebrile and febrile animals. In (2) there was a transient increase in T _hypo of about 0.5 °C at a time corresponding to the start of fever resulting in a significantly smaller fall in T _hypo at the end of the 3-h cooling period (0.5 °C vs 0.9 °C, P < 0.05, n = 5). At this time in both (1) and (2) M was lower than theoretically expected from the increase in shivering threshold during fever. However, most of this effect can be explained when available data showing a decrease in thermosensitivity during S. aureus-induced fever are taken into account. After cessation of cooling in both groups of febrile animals T _hypo rose to about 1 °C higher than the precooling level, which is comparable to the fever level in a separate series of experiments with S. aureus injection without cooling (1.2 °C). Accepted: 23 September 1997     

Molecular Studies on the Microbial Diversity Associated with Mining-Impacted Coeur d’Alene River Sediments

Mass mortalities of larval cultures of Chilean scallop Argopecten purpuratus have repeatedly occurred in northern Chile, characterized by larval agglutination and accumulation in the bottom of rearing tanks. The exopolysaccharide slime (EPS) producing CAM2 strain was isolated as the primary organism from moribund larvae in a pathogenic outbreak occurring in a commercial hatchery producing larvae of the Chilean scallop Argopecten purpuratus located in Bahía Inglesa, Chile. The CAM2 strain was characterized biochemically and was identified by polymerase chain reaction amplification of 16S rRNA as Halomonas sp. (Accession number DQ885389.1). Healthy 7-day-old scallop larvae cultures were experimentally infected for a 48-h period with an overnight culture of the CAM2 strain at a final concentration of ca. 10⁵ cells per milliliter, and the mortality and vital condition of larvae were determined by optical and scanning electron microscopy (SEM) to describe the chronology of the disease. Pathogenic action of the CAM2 strain was clearly evidenced by SEM analysis, showing a high ability to adhere and detach larvae velum cells by using its “slimy” EPS, producing agglutination, loss of motility, and a posterior sinking of scallop larvae. After 48 h, a dense bacterial slime on the shell surface was observed, producing high percentages of larval agglutination (63.28 ± 7.87%) and mortality (45.03 ± 4.32%) that were significantly (P < 0.05) higher than those of the unchallenged control cultures, which exhibited only 3.20 ± 1.40% dead larvae and no larval agglutination. Furthermore, the CAM2 strain exhibited a high ability to adhere to fiberglass pieces of tanks used for scallop larvae rearing (1.64 × 10⁵ cells adhered per square millimeters at 24 h postinoculation), making it very difficult to eradicate it from the culture systems. This is the first report of a pathogenic activity on scallop larvae of Halomonas species, and it prompts the necessity of an appraisal on biofilm-producing bacteria in Chilean scallop hatcheries.     

The viability to a wall shear stress and propagation of <Emphasis Type="Italic">Bifidobacterium longum</Emphasis> in the intensive membrane bioreactor

Bifidobacterium longum grew at 65 L pilot scale of the membrane bioreactor (MBR), externally fitted with ceramic membrane (0.7 m²). Cell mass at the MBR reached 22.18 g L⁻¹ as dry cell weight in 12 h, which is 8.44 times higher than cell mass attained at the vial culture. The growth rate in the vial culture was μ = 0.385 h⁻ and at the batch culture was μ = 1.13 h⁻ in the exponential period and μ = 0.31 h⁻¹ in the stationary period. In the fed-batch mode was μ = 1.102 h⁻¹ for 6 h with inoculation and declined to μ = 0.456 h⁻¹ with feeding of feed medium. The growth rate at the MBR was μ = 0.134 h⁻¹. The number of viable cells was 6.01 × 10¹² cfu L⁻¹ at the batch culture, but increased to 1.15 × 10¹⁴ cfu L⁻¹ at the MBR culture. The specific growth rate of viable cell number (colony-forming units per liter, per hour) improved by 6.01 times from the batch to the MBR culture. The wall shear stress mainly generated by the pump, and the membrane incorporated into the MBR was controlled during the cultivation at the MBR. The viability of B. longum declined to under 10% in the first 2 weeks of the 4-week stability test (40°C) as B. longum was exposed to over wall shear stress 713 Pa, but the viability improved to 30–40% in wall shear stress of 260 Pa or STR culture. The loss in the cell viability can be saved by managing with wall shear stress during the cultivation at the MBR.