Lactic acid bacteria associated with the digestive tract of Atlantic salmon (Salmo salar L.)

The present study reports the effect of excessive handling stress and starvation on the lactic acid bacteria associated with the digestive tract of Atlantic salmon (Salmo salar L.). A relatively low population level (approximately 2 x 103 bacteria per gram wet tissue) of viable adherent heterotrophic bacteria was associated with the digestive tract (foregut, midgut and hindgut). Of the 752 bacterial isolates isolated from diet, water and the digestive tract, 201 isolates belonged to the carnobacteria. Of these isolates, one from the diet, one from the rearing water and 80 from the gastrointestinal tract, were further identified on the basis of 16S rDNA sequence analysis. All these isolates were identified as being Carnobacterium piscicola-like. Daily repeated stress and starvation of the fish over 11 d had no influence on the total culturable bacterial numbers or population level of C. piscicola associated with the digestive tract. C. piscicola-like isolates colonizing the various intestinal regions (foregut, midgut and hindgut) were also screened for their ability to produce growth inhibitory compounds active against the fish pathogen Aeromonas salmonicida. Of the 199 C. piscicola isolates tested, 139 inhibited growth of the pathogen.     

The effect of diet on aerobic bacterial flora associated with intestine of Arctic charr (Salvelinus alpinus L.)

In order to extend the knowledge on the possible effect of diet on the gastrointestinal microbial community of fish, Arctic charr (Salvelinus alpinus L.) were fed diets containing high (23.7%) and low (6.4%) levels of carbohydrate. The number of viable aerobic and facultative aerobic bacteria associated with the digestive tract were not influenced by dietary regimen. A wide range of bacterial species was isolated, and the predominant bacterial species of both rearing groups were identified as Staphylococcus. There were, however, some differences in bacterial composition between the rearing groups, as well as inter-individual variations. For example, atypical Aeromonas salmonicida were isolated from the small and large intestine of two fish fed low dietary carbohydrate, while Aer. caviae-like isolates were found in the small intestine of four fish fed high carbohydrate. Non-motile Aeromonas spp. were found in the rearing group fed high dietary carbohydrate, but at low frequencies. Dietary manipulation seemed to influence the species composition of carnobacteria, Gram-positive rods, oxidase and catalase-negative and fermentative metabolism. Carnobacterium piscicola-like bacteria were only found in the small intestine, while C. mobile-like and Carnobacterium spp. were isolated from the large intestine of fish fed high carbohydrate. On the contrary, C. divergens-like isolates were found associated with the small and large intestine of fish fed low dietary carbohydrate.     

Microbial degradation of oxalate in the gastrointestinal tracts of rats.

Rates of oxalate degradation by mixed bacterial populations in cecal contents from wild rats ranged from 2.5 to 20.6 mumol/g (dry weight) per h. The oxalate-degrading activity in cecal contents from three strains of laboratory rats (Long-Evans, Wistar, and Sprague-Dawley) from four commercial breeders was generally lower, ranging from 1.8 to 3.5 mumol/g (dry weight) of cecal contents per h. This activity did not increase when diets were supplemented with oxalate. When Sprague-Dawley rats from a fifth commercial breeder were fed an oxalate diet, rates of oxalate degradation in cecal contents increased from 2.0 to 23.1 mumol/g (dry weight) per h. Obligately anaerobic, oxalate-degrading bacteria, similar to ruminal strains of Oxalobacter formigenes, were isolated from the latter group of laboratory rats and from wild rats. Viable counts of these bacteria were as high as 10(8)/g (dry weight) of cecal contents, which was less than 0.1% of the total viable population. This report presents the first evidence for the presence of anaerobic oxalate-degrading bacteria in the cecal contents of rats and represents the first direct measurement of the concentration of these bacteria in the large bowel of monogastric animals. We propose that methods used for the maintenance of most commercial rat colonies often preclude the intestinal colonization of laboratory rats with anaerobic oxalate-degrading bacteria.     

Microbial degradation of oxalate in the gastrointestinal tracts of rats

Rates of oxalate degradation by mixed bacterial populations in cecal contents from wild rats ranged from 2.5 to 20.6 mumol/g (dry weight) per h. The oxalate-degrading activity in cecal contents from three strains of laboratory rats (Long-Evans, Wistar, and Sprague-Dawley) from four commercial breeders was generally lower, ranging from 1.8 to 3.5 mumol/g (dry weight) of cecal contents per h. This activity did not increase when diets were supplemented with oxalate. When Sprague-Dawley rats from a fifth commercial breeder were fed an oxalate diet, rates of oxalate degradation in cecal contents increased from 2.0 to 23.1 mumol/g (dry weight) per h. Obligately anaerobic, oxalate-degrading bacteria, similar to ruminal strains of Oxalobacter formigenes, were isolated from the latter group of laboratory rats and from wild rats. Viable counts of these bacteria were as high as 10(8)/g (dry weight) of cecal contents, which was less than 0.1% of the total viable population. This report presents the first evidence for the presence of anaerobic oxalate-degrading bacteria in the cecal contents of rats and represents the first direct measurement of the concentration of these bacteria in the large bowel of monogastric animals. We propose that methods used for the maintenance of most commercial rat colonies often preclude the intestinal colonization of laboratory rats with anaerobic oxalate-degrading bacteria.     

External Microflora of a Marine Wood-Boring Isopod

Bacteria associated with the marine wood-boring isopod Limnoria lignorum were enumerated by acridine orange epifluorescence microscopy and by plate counts on several media; the plate-viable bacteria were isolated and identified. Similar procedures were followed to enumerate and identify bacteria associated with the wood substrate from which the isopods were collected and with the surrounding water from the isopod habitat. Approximately 1.4 × 10⁷ bacterial cells were associated with each individual L. lignorum. Aeromonas hydrophila, Pseudomonas, and Vibrio were the most common genera in the isopod microflora. Wood from L. lignorum burrows had an associated bacterial flora of 1.6 × 10⁷ cells per mg (damp weight). A. hydrophila also predominated in the wood microflora. The water from which the isopod population was collected contained 2.3 × 10⁶ bacteria per ml. Pseudomonas and Vibrio species were very common in the water microflora, but A. hydrophila was not detected. Interactions between the isopod, its associated microorganisms, and the microorganisms within the wood substrate are discussed in the light of the known absence of a resident digestive tract microflora in these animals.     

龙须菜体表附生细菌的几种分离方法比较

采用超声波粉碎法、涡旋振荡法、超声波清洗法、研磨匀浆法等4种不同的方法处理龙须菜,分离其体表的附生细菌,并对分离细菌的数量、种类、形态结构、细胞壁特性等进行了观察和分析。通过对不同方法和相间方法的不同处理所得结果比较显示,超声波清洗法和研磨匀浆法对分离细菌的数量和种类效果都较差;超声波粉碎法和涡旋振荡法效果较好,尤以超声波粉碎法的30W30s处理效果最好,该方法分离到本项目4个方法13个处理获得的16个菌株中的12个菌株,龙须菜的细菌数1．75×10~6cells/g。     

Large intestine bacterial flora of nonhibernating and hibernating leopard frogs (Rana pipiens).

The bacteria in the large intestines of 10 northern leopard frogs (Rana pipiens) were enumerated and partially characterized. Four nonhibernating frogs were collected in the summer, four hibernating frogs were collected in the winter, and two frogs just emerged from hibernation were collected in the spring. All frogs had about 10(10) bacteria per g (wet weight) of intestinal contents and about 10(9) bacteria per g (wet weight) of mucosal scraping, although the counts from the winter frogs were slightly less than those from the other two groups of frogs. Another group of 14 summer frogs, after treatment to induce hibernation, showed a drop in bacterial counts accompanied by a change in the composition of the flora. In most frogs, Bacteroides was the dominant organism. Other bacteria repeatedly isolated at high dilutions were strict anaerobes, including butyrigenic and acetogenic helically coiled bacteria; fusobacteria; and acetogenic, small, gram-positive bacilli. These data indicate that the intestinal flora of frogs is similar to that of mammals and birds and that this flora can be maintained at temperatures close to freezing.     

Digestive tract morphology and digestion in the wombats (Marsupialia: Vombatidae)

Summary Wombats consume grasses and sedges which are often highly fibrous. The morphology of the digestive tract and the sequence of digestion were studied in two species of wombats from contrasting habitats: Vombatus ursinus from mesic habitats and Lasiorhinus latifrons from xeric regions. Studies were performed on wild wombats consuming their natural winter diets, and on captive wombats fed a high-fibre pelleted straw diet. Vombatus had a shorter digestive tract (9.2 vs 12.5 times body length) of greater capacity (wet contents 17.9 vs 13.7% body weight) than Lasiorhinus. The most capacious region of the digestive tract was the proximal colon (62–79% of contents). The proportional length and surface area of the proximal colon were greater in Vombatus, but those of the distal colon were greater in Lasiorhinus. These digestive morphologies may reflect adaptations for greater capacity and longer retention of digesta in Vombatus, but greater absorption and lower faecal water loss in Lasiorhinus. Apparent digestion along the digestive tract was estimated by reference to lignin. The proximal colon was the principal site of fibre and dry matter digestion, whereas nitrogen was mainly digested in the small intestine. Depot fats in captive wombats were highly unsaturated and reflected those in the diet. Therefore, lipids, proteins and soluble carbohydrates in the plant cell contents were digested and absorbed in the stomach and small intestine. Conversely, dietary fibre was probably retained and digested by microbial fermentation along the proximal colon.Abbreviations ADF acid detergent fibre - DM dry matter - NDF neutral detergent fibre - SD standard deviation     

龙须菜体表附生细菌的几种分离方法比较

采用超声波粉碎法、涡旋振荡法、超声波清洗法、研磨匀浆法等4种不同的方法处理龙须菜,分离其体表的附生细菌,并对分离细菌的数量、种类、形态结构、细胞壁特性等进行了观察和分析。通过对不同方法和相间方法的不同处理所得结果比较显示,超声波清洗法和研磨匀浆法对分离细菌的数量和种类效果都较差;超声波粉碎法和涡旋振荡法效果较好,尤以超声波粉碎法的30W30s处理效果最好,该方法分离到本项目4个方法13个处理获得的16个菌株中的12个菌株,龙须菜的细菌数1．75×10⁶cells/g。     

Extracellular polysaccharides produced by cooling water tower biofilm bacteria and their possible degradation

The extracellular polymers (EPS) of biofilm bacteria that can cause heat and mass transfer problems in cooling water towers in the petrochemical industry were investigated. In addition, these microorganisms were screened for their ability to grow and degrade their own EPS and the EPS of other species. Twelve bacteria producing the most EPS were isolated from cooling water towers and characterized biochemically by classic and commercial systems. These were species of Pseudomonas, Burkholderia, Aeromonas, Pasteurella, Pantoea, Alcaligenes and Sphingomonas. EPS of these species were obtained by propan-2-ol precipitation and centrifugation from bacterial cultures in media enriched with glucose, sucrose or galactose. EPS yields were of 1.68-4.95 g l(-1). These EPS materials were characterized for total sugar and protein contents. Their total sugar content ranged from 24 to 56% (g sugar g(-1) EPS), and their total protein content ranged from 10 to 28% (g protein g(-1) EPS). The monosaccharide compositions of EPS were determined by HPLC. Generally, these compositions were enriched in galactose and glucose, with lesser amounts of mannose, rhamnose, fructose and arabinose. All bacteria were investigated in terms of EPS degradation. Eight of the bacteria were able to utilize EPS from Burkholderia cepacia, seven of the bacteria were able to utilize EPS from Pseudomonas sp. and Sphingomonas paucimobilis. The greatest viscosity reduction of B. cepacia was obtained with Pseudomonas sp. The results show that the bacteria in this study are able to degrade EPS from biofilms in cooling towers.     

The effect of antimicrobial compounds on the gastrointestinal microflora of rainbow trout, Salmo gairdneri Richardson

Populations of aerobic and anaerobic heterotrophic bacteria occurring in the gastrointestinal tract of healthy rainbow trout were estimated using a dilution plate technique. Data revealed a progressive decline in numbers of aerobic bacteria along the digestive tract from oesophagus to lower intestine. However, the highest numbers were recovered from the intestinal contents and faeces. Anaerobes were generally restricted to the upper intestine and intestinal contents. The aerobic component of the bacterial microflora from the digestive tract was equated with Acinetobacter calcoaceticus, Aeromonas hydrophila, Bacillus circulans, Bac. megaterium , coryneforms, Grampositive irregularly shaped rods, Flavobacterium sp., Kurthia sp., Microhacterium sp., Providencia stuartii, Pseudomonas spp., Ps.fluorescens and Ps. pseudoalcaligenes . Evidence from scanning electron microscopy pointed to a general lack of colonization of the gut wall: instead, microorganisms were abundant in the intestinal contents. Antimicrobial compounds, i.e. oxolinic acid, oxytetracycline and sulphafurazole (which are commonly used to combat infections by Gramnegative bacterial fish pathogens), caused an increase in bacterial numbers throughout the digestive tract, with maximal numbers in the lower intestine. The bacteria, comprising an essentially different range of taxa, were generally resistant to the antibiotics in use. Conversely, erythromycin and penicillin G, which are used to treat some diseases caused by Gram-positive bacteria, caused a rapid reduction in bacterial numbers within the gastrointestinal tract.     

Bacteria Associated with the Gills of Salmonid Fishes in Freshwater

The bacteria on the gills of 7 species of freshwater salmonid fishes were examined qualitatively and quantitatively. Both wild and hatchery cultured salmonids were examined. The former were obtained from 12 different locations in British Columbia. Species of Pseudomonas and Cytophaga predominated on both groups of fish. The microflora of the wild fish also contained Aeromonas and members of the Brevibacterium –coryneform– Erysipelothrix group. The microflora of cultured fish was less varied. As many as 10⁶ viable organisms/g wet weight of gill tissue were recovered.     

Bacterial flora of the sea urchin Echinus esculentus.

A total of 85 isolates of mesophilic, aerobic, heterotrophic bacteria were isolated from the gut, peristomial membrane, and coelomic fluid from specimens of the sea urchin Echinus esculentus from the Clyde Sea area of Scotland. These isolates were compared with 26 isolates from sand and seawater in the same locality. Overall, strains of Pseudomonas and Vibrio predominated. Gut (with an average bacterial viable count of 2 X 10(7) per 3-cm section) and coelomic fluid (which was often sterile and rarely had more than 40 bacteria per ml) had similar distributions of genera, with Vibrio predominating and Pseudomonas and Aeromonas next in abundance. In contrast, the flora of the peristomial membrane (with an average count of detachable bacteria of 2.5 X 10(5) per membrane) resembled that of sand/seawater in having Pseudomonas predominating, gram-positive forms or Vibrio next in abundance, and smaller numbers of Aeromonas, Flavobacterium, Acinetobacter, and Moraxella.     

Isolation and characterization of moderately halophilic bacteria from fully cured salted cod (bachalao)

A total of 128 Strains of moderately halophilic bacteria were isolated from wet, dry and desalted bachalao (salted codfish) as well as from fresh cod and curing salt. The viable count of these bacteria in fully cured wet and dry bachalao ranged from 10³ to 10⁷ per g. All strains were characterized with 40 phenotypic tests and clustered using the S _SM coefficient and UPGMA linking analysis. The strains clustered into five phena at 75% similarity, with 77 strains in phenon A and 37 in phenon E. Two main colony types, smooth and rough, were observed and correspond to phena A, B and C on one hand and phenon E on the other. These two types seem to represent the dominating bacterial flora in fully cured, wet and dry bachalao, respectively. Representative strains of the smooth colony type were characterized further and found to grow well in 0.1–4.5 mol I⁻¹ NaCl and at 15–37°C. They have not, at present, been assigned to any known bacterial species.     

The bacterial flora of the intestine of Ascaris suum and 5-hydroxytryptamine production

Representative facultative anaerobes of the bacterial flora from the intestine of female Ascaris suum were isolated and identified. The number of bacteria in the intestine was approximately 4 X 10(9) per g wet weight of intestine. Seventeen of 19 of the isolated colonies were found to secrete 5-hydroxytryptamine in culture. Holding A. suum in an antibiotic-containing medium did not affect the levels of 5-hydroxytryptamine in the worm, which were 231 +/- 14 ng/g in antibiotic-media as compared to 250 +/- 16 ng/g in control media. This implied that the bacteria may not be contributing to the level of 5-hydroxytryptamine in the tissues of A. suum.     

Luminous Enteric Bacteria of Marine Fishes: a Study of Their Distribution, Densities, and Dispersion

Three taxa of luminous bacteria (Photobacterium fischeri, P. phosphoreum, and Beneckea spp.) were found in the enteric microbial populations of 22 species of surface- and midwater-dwelling fishes. These bacteria often occurred in concentrations ranging between 10⁵ and 10⁷ colony-forming units per ml of enteric contents. By using a genetically marked strain, it was determined that luminous cells entering the fish during ingestion of seawater or contaminated particles traversed the alimentary tract and survived the digestive processes. After excretion, luminous bacteria proliferated extensively on the fecal material and became distributed into the surrounding seawater. Thus, this enteric habitat may serve as an enrichment of viable cells entering the planktonic luminous population.     

Use of 16S rRNA gene-targeted group-specific primers for real-time PCR analysis of predominant bacteria in human feces

16S rRNA gene-targeted group-specific primers were designed and validated for specific detection and quantification of the Clostridium leptum subgroup and the Atopobium cluster. To monitor the predominant bacteria in human feces by real-time PCR, we used these specific primers together with four sets of group-specific primers for the Clostridium coccoides group, the Bacteroides fragilis group, Bifidobacterium, and Prevotella developed in a previous study (T. Matsuki, K. Watanabe, J. Fujimoto, Y. Miyamoto, T. Takada, K. Matsumoto, H. Oyaizu, and R. Tanaka, Appl. Environ. Microbiol. 68:5445-5451, 2002). Examination of DNA extracted from the feces of 46 healthy adults showed that the C. coccoides group was present in the greatest numbers (log10 10.3 +/- 0.3 cells per g [wet weight] [average +/- standard deviation]), followed by the C. leptum subgroup (log10 9.9 +/- 0.7 cells per g [wet weight]), the B. fragilis group (log10 9.9 +/- 0.3 cells per g [wet weight]), Bifidobacterium (log10 9.4 +/- 0.7 cells per g [wet weight]), and the Atopobium cluster (log10 9.3 +/- 0.7 cells per g [wet weight]). These five bacterial groups were detected in all 46 volunteers. Prevotella was found in only 46% of the subjects at a level of log10 9.7 +/- 0.8 cells per g (wet weight). Examination of changes in the population and the composition of the intestinal flora for six healthy adults over an 8-month period revealed that the composition of the flora of each volunteer remained stable throughout the test period.     

Removal of bacteria from water by adhesion to cross-linked poly(vinylpyridinium halide).

Cross-linked poly(vinylpyridinium halide) was found to have a novel and remarkable ability to remove bacteria from water. For example, when 10 g (wet weight) of cross-linked poly(N-benzyl-4-vinylpyridinium bromide) was contacted with 20 ml of suspensions of Escherichia coli (9.7 X 10(4) to 9.7 X 10(7)/ml), Salmonella typhimurium (8.0 X 10(6) to 1.1 X 10(7)/ml), Streptococcus faecalis (5.0 X 10(7)/ml), Staphylococcus aureus (8.1 X 10(7)/ml), and Pseudomonas aeruginosa (3.2 X 10(5)/ml) under stirring in sterilized physiological saline at 37 degrees C, 99% of the viable cells of these bacteria were removed in 2 to 6 h. When suspensions of these bacteria (10(5) to 10(8) cells per ml) were passed through a column (20 mm by 100 cm) of cross-linked poly(N-benzyl-4-vinylpyridinium bromide) at 37 degrees C with a flow rate of 0.8 to 1.4 bed volumes per h, 97 to 100% of the viable cells were eliminated from the suspensions during the treatment. Mechanistic studies demonstrated that cross-linked poly(vinylpyridinium halide) irreversibly captured these bacteria alive during the treatment. That is, total organic carbon was removed during the treatment, and the bacteria which adhered to the resin proliferated on the bacterial medium. The adhesion capacity was estimated to be 10(10) cells per g (dry weight). Total organic carbon was also removed even when the bacteria were killed by heat treatment before the column studies.     

Occurrence of Potential Pathogens in Water Containing Ornamental Fishes

The bacterial population of the water supplied with ornamental fish purchased from retail outlets was examined qualitatively and quantitatively. As many as 10(9) viable aerobic organisms per 100 ml were present, with fecal coliform counts as high as 10(5) per 100 ml. Citrobacter, Escherichia, Pseudomonas, and Vibrio were isolated from 75% or more of the samples, whereas Aeromonas, Alcaligenes, Enterobacter, Flavobacterium, and Streptococcus were isolated from 45 to 65% of the samples. Pseudomonas aeruginosa, Edwardsiella tarda, and Klebsiella pneumoniae were also isolated.     

Bacteria in bivalve shellfish with special reference to the oyster

The bacterial flora of the Pacific oyster Crassostrea gigas, the sea mussel Perna viridis and the arkshell clam Scapharca cornea differed considerably from that of seawater in both numbers and generic composition. The numbers of heterotrophic bacteria in the bivalve shellfish, including the anaerobes and spore-forming bacteria, were greater than that in the surrounding water. Pseudomonas spp. were the dominant organisms, comprising over one third of the 321 strains characterized after isolation from the bivalves and seawater. Other bacteria isolated from the shellfish included Vibrio, Acinetobacter, and Aeromonas spp., whereas the seawater flora consisted mainly of coliform organisms, coryneform bacteria and Flavobacterium/Cytophaga spp. Bacteria associated with the deposit-feeding clams were higher in density and more distinct in generic composition as compared with those in the suspension-feeding oysters and mussels. Over 90% of the coliform and heterotrophic bacteria in oysters were found in organs associated with the digestive tract. Coliforms were mainly found in the stomach while heterotrophs were present in both stomach and the lower intestine. The results suggest that the stomach flora of oysters are mainly derived from the external environment and, through a process of selection and multiplication, that it may be gradually replaced by a more indigenous population which dominates the lower digestive tract.