Carbon Monoxide Oxidation by Bacteria Associated with the Roots of Freshwater Macrophytes

The potential rates and control of aerobic root-associated carbon monoxide (CO) consumption were assessed by using excised plant roots from five common freshwater macrophytes. Kinetic analyses indicated that the maximum potential uptake velocities for CO consumption ranged from 0.4 to 2.7 μmol of CO g (dry weight)⁻¹ h⁻¹ for the five species. The observed rates were comparable to previously reported rates of root-associated methane uptake. The apparent half-saturation constants for CO consumption ranged from 50 to 370 nM CO; these values are considerably lower than the values obtained for methane uptake. The CO consumption rates reached maximum values at temperatures between 27 and 32°C, and there was a transition to CO production at ≥44°C, most likely as a result of thermochemical organic matter decomposition. Incubation of roots with organic substrates (e.g., 5 mM syringic acid, glucose, alanine, and acetate) dramatically reduced the rate of CO consumption, perhaps reflecting a shift in metabolism by facultative CO oxidizers. Based on responses to a suite of antibiotics, most of the CO consumption (about 90%) was due to eubacteria rather than fungi or other eucaryotes. Based on the results of acetylene inhibition experiments, methanotrophs and ammonia oxidizers were not active CO consumers.     

Features of the Changes in External Morphology and Axial Skeleton in Juvenile Salmonid Fishes (Salmonidae) Associated with Smoltification

Journal of Ichthyology - Changes in external morphological characters and relative lengths of vertebral centra from different regions of the vertebral column are analyzed during smoltification in...     

Arsenic Bioaccumulation in Freshwater Fishes

The arsenic ambient water quality criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 μ g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based on two data points for oysters and fish that was proposed by the U.S. Environmental Protection Agency in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration. In the nearly quarter of a century since this BCF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. From this database, we identified 12 studies of arsenic bioaccumulation in freshwater fishes in order to explore differences in laboratory-generated BCFs and field-generated bioaccumulation factors (BAFs) and to assess their relationship to arsenic concentrations in water. Our analysis indicates that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water. A power function indicates that the highest BCF values may occur at low background levels and may decrease as environmental concentrations increase above the ambient range.     

Ferric Iron Reduction by Bacteria Associated with the Roots of Freshwater and Marine Macrophytes

In vitro assays of washed, excised roots revealed maximum potential ferric iron reduction rates of >100 μmol g (dry weight)⁻¹ day⁻¹ for three freshwater macrophytes and rates between 15 and 83 μmol (dry weight)⁻¹ day⁻¹ for two marine species. The rates varied with root morphology but not consistently (fine root activity exceeded smooth root activity in some but not all cases). Sodium molybdate added at final concentrations of 0.2 to 20 mM did not inhibit iron reduction by roots of marine macrophytes (Spartina alterniflora and Zostera marina). Roots of a freshwater macrophyte, Sparganium eurycarpum, that were incubated with an analog of humic acid precursors, anthroquinone disulfate (AQDS), reduced freshly precipitated iron oxyhydroxide contained in dialysis bags that excluded solutes with molecular weights of >1,000; no reduction occurred in the absence of AQDS. Bacterial enrichment cultures and isolates from freshwater and marine roots used a variety of carbon and energy sources (e.g., acetate, ethanol, succinate, toluene, and yeast extract) and ferric oxyhydroxide, ferric citrate, uranate, and AQDS as terminal electron acceptors. The temperature optima for a freshwater isolate and a marine isolate were equivalent (approximately 32°C). However, iron reduction by the freshwater isolate decreased with increasing salinity, while reduction by the marine isolate displayed a relatively broad optimum salinity between 20 and 35 ppt. Our results suggest that by participating in an active iron cycle and perhaps by reducing humic acids, iron reducers in the rhizoplane of aquatic macrophytes limit organic availability to other heterotrophs (including methanogens) in the rhizosphere and bulk sediments.     

Intracellular Symbiosis and Energetic Role of Bacteria in Gill Epithelium of Freshwater Mollusks and Fishes

Penetration of bacteria by endocytosis into gill epithelial cells has been revealed in animals of different evolutionary levels (freshwater mollusks and fishes). These data confirm the leading role of endosymbiosis in the origin of eukaryotes from prokaryotes and in the evolution of animal life.     

Community Structure of Bacteria Associated with Sheaths of Freshwater and Brackish Thioploca Species

Bacterial communities associated with sheaths of Thioploca spp. from two freshwater lakes (Lake Biwa, Japan, and Lake Constance, Germany) and one brackish lake (Lake Ogawara, Japan) were analyzed with denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The comparison between the DGGE band patterns of bulk sediment and Thioploca filaments of Lake Biwa suggested the presence of specific bacterial communities associated with Thioploca sheaths. As members of sheath-associated communities, bacteria belonging to Bacteroidetes were detected from the samples of both freshwater lakes. A DGGE band from Thioploca of Lake Biwa, belonging to candidate division OP8, was quite closely related to another DGGE band detected from that of Lake Constance. In contrast to the case of freshwater lakes, no bacterium of Bacteroidetes or OP8 was detected from Thioploca of Lake Ogawara. However, two DGGE bands from Lake Ogawara, belonging to Chloroflexi, were quite closely related to a DGGE band from Lake Constance. Two DGGE bands obtained from Lake Biwa were closely related to phylogenetically distant dissimilatory Fe(III)-reducing bacteria. Cloning analyses for a dissimilatory sulfite reductase gene were performed on the same samples used for DGGE analysis. The results of the analyses suggest that sheaths of freshwater/brackish Thioploca have little ecological significance for the majority of sulfate reducers.     

On the Mutation Rates of the Mitochondrial and Nuclear Genomes of Salmonid Fishes

Mutation rates of the mitochondrial and nuclear genomes of salmonid fishes were assessed on the basis of a phylogenetic study of 12 species representing four genera of the family Salmonidae. Analysis of the extent of divergence of the masu salmon Oncorhynchus masou and the Pacific trout Parasalmo suggests a high rate of mtDNA mutation in the masu salmon. However, the nuclear genome in this species has mutated relatively slowly. For the other 5 species of Pacific salmon, no discrepancy was found in the mutation rates of mitochondrial and nuclear DNA. Values of the absolute time of divergence of taxa, calculated for the two independently inherited parts of the salmonid genome, were approximately within the same range and coincided with those based on evolutionary hypotheses [1, 21].     

Cable Bacteria in Freshwater Sediments

In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage.     

Special Adaptive Problems Associated with Unisexual Fishes

SYNOPSIS. Two genera of fishes, Poecilia and Poeciliopsis, bothin the family Poeciliidae, have established unisexual populations.One "species," Poecilia formosa, is a diploid form that reliesupon sperm from Poecilia latipinna or P. mexicana to initiateparthenogenetic development (gynogenesis). Triploid individualsof P. formosa have also been discovered but the mode of reproductionand the significance of such fish to natural populations haveyet to be established. In the genus Poeciliopsis three gynogenetic triploids are known.Each is superimposed on a different bisexual host: Poeciliopsislucida, P. monacha or P. viriosa. Five diploid hybridogeneticformsalso have been identified. These are fertilized by either P.lucida, P. latidens, or P. occidentalis. In hybridogenetic forms,sperm actually feitilizes the egg. A hybrid with maternal andpaternal characters is produced, but only maternal genes aretransmitted through the egg to the next generation. Because of their sperm dependency, all unisexual fishes mustreside with at least one of the parental species. They areforcedto compete with them for sperm, space, and other limited resources.The ability to produce two females for every one that bisexualsproduce suggests that the unisexuals have the potential to winthis competition; but in so doing, they would lose their sexualsupport and eliminate themselves. A density-dependent mate selectionsystem plays a role in establishing a workable balance betweenthe competing elements. Unisexual forms of both Poecilia and Poeciliopsis are of hybridorigin. For most of them, the parental precursors and the proportionof genetic material that each contributed to the unisexual isknown. The various genomes that make up the unisexuals are adaptedto a variety of habitats. Once these genomes are combined ina unisexual hybrid, potential for adaptation to multiple nichesexists; this coupled with heterosis contributes greatly to thesuccess of gynogenetic and hybridogenetic fishes.     

Isolation of Lactic Acid Bacteria from Intestine of Freshwater Fishes and Elucidation of Probiotic Potential for Aquaculture Application

Probiotics and Antimicrobial Proteins - Probiotics play significant roles in enhancing systemic immunity, improving intestinal balance and feed value, enhancing enzymatic digestion, and inhibiting...     

Patterns of Freshwater Fishes of the Caribbean Versant of Venezuela

We delineate local and regional biogeographic provinces that suggest patterns of species richness, and primary and secondary freshwater fish distributions along the Caribbean coast of Venezuela. We use presence‐absence records and classification and ordination models. Patterns at local and regional scales varied markedly such that primary species dominated humid drainages and secondary species dominated arid drainages or transition provinces. Species rich areas, and the presence of narrowly endemic species correlate with patterns of historical isolation and hydrographic refuges. Patterns of species distributions across arid drainages suggest that close proximity of coastal marine drainages allows dispersion and exchange of species. This pattern is particularly evident among secondary species. Hotspots of species richness and endemisms are identified and are recommended as priorities for conservation (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Distribution Patterns of Indigenous Freshwater Fishes in the Tagus River Basin, Spain

Classification and ordination methods used to examine the internal complexity of the Mediterranean Tagus River catchment based on fish distribution revealed that it is not a homogeneous biogeographical unit. The indigenous fishes analyzed in this study are distributed through the basin forming geographical communities (chorotypes), some of which are associated with environmental factors like river morphology, water quality or geographical location. Nevertheless, 40% of the variation in species occurrence remains unexplained by either environmental or geographical variables, suggesting that historical factors may influence the freshwater fish distribution patterns. Three main biogeographical areas, delimited by significant boundaries, were identified. Two of them are identified as the upper and the middle-lower basins of the Tagus River catchment; the third corresponds to the Alagón River and seems to be linked to historical factors of the catchment.     

Bacteria Associated with Immunoregulatory Cells in Mice

This study examined bacteria-immune interactions in a mouse model possessing microbiota-dependent immune regulatory features similar to those occurring in human atopy, colitis, and immune regulation. Associations between the abundance of several bacterial phylotypes and immunoregulatory target cell types were identified, suggesting that they may play a role in these phenotypes.Bacteria are involved in critical aspects of immune system development and regulation (5, 23, 26, 29). Mice raised under germfree conditions exhibit a variety of abnormalities, including hypoplastic Peyer''s patches, reduced numbers of IgA-producing cells, relatively unstructured spleen and lymph nodes, and hypogammaglobulinemic serum (23). Remarkably, after several weeks of exposure to standard intestinal microbiota, normal immune structure and function are restored. Mechanistic details underlying microbe-immune interactions have been recently elucidated for two common intestinal bacteria. Bacteroides thetaiotaomicron was shown to induce the angiogenin Ang4, a component of innate immunity possessing microbicidal activity against a wide range of intestinal microbes, including both bacterial and fungal pathogens (16). In addition, studies of the Bacteroides fragilis zwitterionic capsular polysaccharide A have established it as a cognate antigen of certain CD4⁺ T cells, which programs immune effector polarization (24) and protection of mice from infection by Helicobacter hepaticus through several immune-mediated mechanisms (25). Resident microbiota also modify the interaction of dendritic cells with regulatory T-cell populations, with resultant susceptibility to chronic inflammatory disease, like colitis (15, 28).Recent work by Braun and colleagues has characterized a mouse model with unique immunologic features linking resident microbiota with levels of regulatory CD8⁺ T cells (13, 17, 39). This model is comprised of two physically isolated colonies of isogenic mice harboring distinct microbial communities: conventional floras (CF) and restricted floras (RF). CF refers to C57BL/6 mice housed in a standard specific-pathogen-free facility, while RF refers to C57BL/6 mice containing a different complement of intestinal microorganisms (13, 30), originally created by transferring several nonpathogenic anaerobic bacteria into antibiotic-treated mice (13). RF mice differ from CF mice in several immunologic phenotypes, including selective reduction of marginal zone (MZ) B cells (39), plasmacytoid dendritic cells (pDC) (13), and invariant natural killer (iNK) T cells (38a), as well as naïve CD4⁺ and CD8⁺ T cells (17). In addition, RF mice were shown to be resistant to colitis under genetic or adoptive transfer conditions that permit disease activity in CF mice (2). RF mice also cleared experimental infections by Campylobacter jejuni more slowly than did their CF counterparts (6). The resulting concept is that certain resident microbiota, which may be more abundant in RF mice than in CF mice, induce invariant Qa-1 T cells, with resultant changes in host immunoregulation and microbial surveillance (2).An important issue raised by the foregoing observations is the identity of resident microbiota responsible for this host immunoregulatory response. The objective of this study was to develop a methodology, based on bacteria-immune interactions in the RF/CF mouse model, to identify candidate microbiota. In this study, we employed a series of experiments examining associations between the population densities of bacterial rRNA genes and several immunologic features that differ between CF and RF mice.     

Production and Consumption of Biotin by the Intestinal Microflora of Cultured Freshwater Fishes

Effects of twelve flavonoids and five catechins as well as gallic acid on two kinds of glutathione-related enzymes were investigated. Glutathione 5-transferase (EC 2.5.1.18) activity was measured by S-2,4-dinitrophenyl glutathione formation from 1-chloro-2,4-dinitrobenzene and reduced glutathione. Glutathione reductase (EC 1.6.4.2) activity was followed by NADPH dehydrogenation. Fisetin and myricetin were potent inhibitors of glutathione S-transferase, while kaempferol, quercetin, baicalein, and quercitrin were medium inhibitors. Epicatechin gallate and epigallocatechin gallate also showed medium inhibition. Kinetic analyses indicated that fisetin was a mixed type inhibitor of glutathione S-transferase with respect to both substrates, while myricetin was a competitive inhibitor of the same enzyme with both substrates. Fisetin and myricetin were noncompetive inhibitors of glutathione reductase with both NADPH and oxidized glutathione. The inhibition patterns of GT and GR as well as the results of kinetic analyses indicated a possibility that inhibitory flavonoids might have some influence on the glutathione recognition sites of the two enzymes.     

Symbiotic Bacteria in Gills and Guts of Chinese Mitten Crab (Eriocheir sinensis) Differ from the Free-Living Bacteria in Water

Aquatic animals have a close relationship with water, but differences in their symbiotic bacteria and the bacterial composition in water remains unclear. Wild or domestic Chinese mitten crabs (Eriocheir sinensis) and the water in which they live were collected from four sampling sites in Jiangsu and Shanghai, China. Bacterial composition in water, gills or guts of E. sinensis, were compared by high-throughput sequencing using 16S rRNA genes. Analysis of >660,000 sequences indicated that bacterial diversity was higher in water than in gills or guts. Tenericutes and Proteobacteria were dominant phyla in guts, while Actinobacteria, Proteobacteria and Bacteroidetes were dominant in gills and water. Non-metric multidimensional scaling analysis indicated that microbiota from gills, guts or water clearly separated into three groups, suggesting that crabs harbor a more specific microbial community than the water in which they live. The dominant OTUs in crab gut were related to Mycoplasmataceae, which were low in abundance in gills, showing that, like mammals, crabs have body-site specific microbiota. OTUs related to Ilumatobacter and Albimonas, which are commonly present in sediment and seawater, were dominant in gills but almost absent from the sampled water. Considering E. sinensis are bottom-dwelling crustacean and they mate in saline water or seawater, behavior and life cycle of crabs may play an important role in shaping the symbiotic bacterial pattern. This study revealed the relationship between the symbiotic bacteria of Chinese mitten crab and their habitat, affording information on the assembly factors of commensal bacteria in aquatic animals.     

PKX,the Causative Agent of Proliferative Kidney Disease (PKD) in Pacific Salmonid Fishes and Its Affinities with the Myxozoa1

Proliferative kidney disease (PKD), caused by an unclassified protozoan (PKX), is reported from Pacific salmon, Oncorhynchus tshawytscha (Walbaum) and O. kisutch (Walbaum), and steelhead trout, Salmo gairdneri Richardson, held at the Mad River Hatchery in California, USA. The cumulative mortality attributed to the disease was 95, 13, and 18% respectively. The mortalities were greatest at mean water temperatures of 12-14°C during July 1983. The ultrastructure of the PKX organism and its associated pathology during clinical disease in all three species were consistent with those of the parasite in rainbow trout (Salmo gairdneri) as described in European outbreaks. Significant mortalities did not occur after August, at which time the parasite could no longer be detected in the salmon species. The steelhead continued to exhibit parasites in the kidney interstitium and epithelium and lumens of the tubules. Myxosporidan trophozoites and developing spores were also observed in the lumens of the kidney tubules of these fish. Although a mixed infection with another parasite may have occurred, evidence suggests that the myxosporidans are later stages of PKX. They were only observed in fish exposed to water with the infective stage and were particularly prominent in recovering fish. The PKX organism is similar to UBO, an unclassified protozoan of carp suspected to be an early stage of Sphaerospora renicola Dyková & Lom. Both parasites infect the blood and kidney, divide by endogeny, and are released by disintegration of the primary mother cell. The intraluminal myxosporean forms show similarities to Sphaerospora spp. in that they are monosporous and sporoblasts are formed within pseudoplasmodia. It is possible that PKX migrates to the lumen of the kidney tubule and subsequently sporulates. If the myxosporean forms are later stages of PKX, then it would belong to the phlyum Myxozoa.     

The Distribution and Origins of Freshwater Fishes in the Balkan Peninsula,Especially in Greece

Zoogeography of freshwater fish fauna of the Balkan peninsula south of the Danube has been studied. Four main divisions - Ponto-Aegean, Attiko-Beotia, Dalmatia and South Adriatic-Ionian - were recognized. All endemics belong to European, Euro-Siberian or Palaearctic taxa, originated from ancestors of the Euro-Siberian stock and reached the area as well as Asia Minor in Oligocene or Miocene. Central European and Danubian species are intruders of late Pliocene to Pleistocene arriving by the freshened Black Sea and its drainage basin or directly from the North (Middle Danube) by river captures.