Characterization and finding the origin of off-flavor compounds in Nile tilapia cultured in net cages in hydroelectric reservoirs, São Paulo State, Brazil.

An increasing demand for fish products has led to an intensive aquaculture production in Brazil, and cultivation of fish constituted 860 × 103 tons in 2022, contributing to the 87% of total fish consumption. Nile tilapia constitutes almost half of the aquaculture production, and most tilapia farms use floating net cages. One of the major constraints of intensive fish production is production of off-flavors. Release of nutrients by the fish leads to deterioration of the water quality and stimulates growth of microorganisms, also including off-flavor producing species. The objective of this study was to determine levels of taste and odor compounds (geosmin, 2-MIB and a selection of volatile compounds) and their impact on the flavor quality of Nile tilapia produced in net cages in reservoirs in São Paulo State, Brazil. GC-MS analysis of fish and water from six different farms showed concentrations of geosmin in the water from 1 to 8 ng/L, while geosmin in fish flesh ranged from 40 to 750 ng/kg. The level of 2-MIB in water was 2 to 25 ng/L, and 0 to 800 ng/kg fish. The GC-MS analysis also revealed presence of more than 100 volatile organic compounds in the fish flesh, consisting of aldehydes, alcohols, benzene derivatives, hydrocarbons, ketones and few other compounds. Geosmin and 2-MIB related flavor notes were detected in all fish by a sensory panel, and a high correlation between the chemical and sensory analyses was found. The potential impact of the volatile organic compounds on the fish flavor is discussed. Analysis of the water quality in the reservoirs indicated that levels of geosmin and 2-MIB levels were highly influenced by the nutrient levels in the water.

Volatiles produced by Streptomyces spp. delay rot in apples caused by Colletotrichum acutatum.

Volatile organic compounds (VOCs) produced by microorganisms may prevent postharvest rot in fruits. Here, it was examined if VOCs from different species of Streptomyces can control infection in apples caused by the fungal pathogen Colletotrichum acutatum. Incubation of C. acutatum-infected apples in semi-closed boxes with actively growing strains of three Streptomyces (S. coelicolor, S. diastatochromogenes and Streptomyces strain 2R) showed that VOCs reduced rot areas of the apples by 45-66% after 8 days and 39-57% after 10 days, relative to infected apples incubated without Streptomyces. No differences in inhibition among the three strains were seen. In contrast, a mutant strain of Streptomyces that lacks major genes involved in biosynthesis of secondary metabolites, did not reduce development of rot in the apples. Furthermore, Streptomyces VOCs reduced radial hyphal growth of C. acutatum on agar. Several of the VOCs produced by three Streptomyces strains have previously shown fungicidal properties. Although the specific VOCs being active in inhibition of C. acutatum remain to be determined, VOCs may have a great potential as biofumigants to minimize postharvest diseases in fruits.

Monitoring of saxitoxin production in lakes in Denmark by molecular, chromatographic and microscopic approaches.

Diversity of phytoplankton in three eutrophic and two mesotrophic lakes in Denmark was determined by microscopic and HPLC pigment analyses to identify and quantify potential saxitoxin (STX) producing cyanobacteria. Potential dominant STX-producers were identified to the filamentous genera Dolichospermum, Cuspidothrix, Phormidium and Planktolyngbya. Presence of STX production was documented by extraction of five intracellular STXs that included (in declining concentration in the cyanobacteria) dc-neo-STX, neo-STX, dc-STX, STX and GTX. Total concentrations of the five STXs varied from 9 to 142 fg per potential STX producer, corresponding to 87 to 985 ng L-1 in the lakes. For molecular detection of the STX-producers, a quantitative PCR method was developed by design of a new robust primer set with broad coverage to target the sxtA gene that is common to all STX-producing cyanobacteria. After validation, copy numbers of the sxtA gene were determined to vary from about 104 (mesotrophic lakes) to 108 per mL (the most eutrophic lake). A moderate but significant correlation was observed between abundance of the sxtA copies and concentrations of the five intracellular STXs. The qPCR assay was found to be a rapid and robust procedure for quantification of STX producers. Saxitoxin and its analogs appeared not to cause health concerns in the lakes, but commercial fishing for pike perch in the most eutrophic lake should be monitored to test for food web accumulation of STXs.

Occurrence of Cyanobacteria and microcystins in hydroelectric reservoirs used for fish farming.

Fish farming can have a negative impact on water quality and aquatic organisms due to emerging blooms of Cyanobacteria and the production of cyanotoxins. In this study, the effect of aquaculture in hydroelectric reservoirs in Brazil was evaluated in six fish farms and in upstream and downstream water through analysis of the microbiome, Cyanobacteria and microcystin concentrations. Synechococcus and Microcystis were observed at all six locations, while Limnothrix was also observed abundantly at two locations. An increase in the relative abundance of Cyanobacteria inside the fish farms was observed at two locations, while an increase of Cyanobacteria was observed in downstream at five of the six locations. Microcystins were detected in significant and high values in all locations, with concentrations up to 1.59 µg/L. The trend in microcystin concentrations was mirrored in copy numbers of the mcyE gene (encodes microcystin synthetase) and presence of Microcystis, but not in any of the other observed cyanobacterial groups. In summary, the study shows that aquaculture production influenced the water microbiome inside and downstream the fish farms, and a direct correlation was found between mcyE gene copies, microcystin production and abundance of Microcystis, but not for the total abundance of Cyanobacteria.

Microbial Production of the Off-Flavor Geosmin in Tilapia Production in Brazilian Water Reservoirs: Importance of Bacteria in the Intestine and Other Fish-Associated Environments.

AIM: To determine major sources of microbially produced geosmin in the commercially important aquaculture fish species tilapia. METHODS AND RESULTS: Abundance and composition of geosmin-producing bacteria in water and fish biosphere (intestine, digesta, and fins) of Nile tilapia (Oreachromis niloticus) raised in net cages in Brazilian freshwater farms were examined. By combining qPCR of the geosmin synthase geoA gene and 16S rRNA gene amplicon sequencing to identify potential geosmin-producing organisms, we observed that the proportion and composition of geosmin producers appeared to be rather similar in the water, digesta, intestinal mucous, and on skin, making up about 0.1-0.2% of the total bacterial densities. A high proportion of Cyanobacteria and other putative geosmin producers affiliated to the Actinomycetales were identified in the intestinal mucous layer. The main uptake site for geosmin in fish is traditionally assumed to be through the gill surface, but the present results suggest that uptake by the intestinal tract may represent a major source of geosmin uptake in fish. CONCLUSION: The high abundance of geosmin-producing bacteria in the intestinal mucous layer and digesta may indicate that the digestive system in fish is an important, but hitherto overlooked, source of geosmin and likely other off-flavors in fish. SIGNIFICANCE AND IMPACT OF STUDY: Tainting of fish by microbially produced off-flavors spoils fish quality and lowers consumer preferences for aquaculture-produced freshwater fish. Our results highlight the potential for the application of probiotic microorganisms for management of the intestinal microflora to improve the fish quality. HIGHLIGHTS: -Off-flavor producing bacteria are widely abundant in aquaculture.-Off-flavor producers found on skin surface of fish.-Off-flavor producing bacteria accumulate in the digestive system.-Off-flavor producers might release significant amounts of off-flavor during lysis in the gut.-Off-flavor uptake through the digestive system might be quantitatively significant.

Ballast water treatment and bacteria: Analysis of bacterial activity and diversity after treatment of simulated ballast water by electrochlorination and UV exposure.

Effects of ballast water (BW) treatment by ultra-violet (UV) light and electrochlorination (EC) on survival, activity and diversity of marine bacterioplankton and release of organic matter from cell damage were examined at discharge in a large-scale BW test facility (250 m3 tanks) at Hundested harbour, Denmark. The tests were performed in accordance with the requirements for type approval testing by International Maritime Organization (IMO) and US Coast Guard. After treatment, the water was held in the tanks for one day (EC) before discharge, or 6 days (UV, including also a final UV re-treatment) before discharge. In the discharged and treated water, numbers of viable bacteria and bacterial growth rate had decreased significantly relative to the untreated water, but the total number of bacteria only was reduced in the EC-treated water. After additional storage for up to 10 days in small-scale laboratory incubations, significant regrowth of bacteria was observed after either treatment. Sequencing of 16S rRNA gene amplicons demonstrated that α-Proteobacteria initially were dominant, but γ-Proteobacteria dominated after regrowth. Bacteria used to document BW treatment efficiency (E. coli, Vibrio spp., enterococci) survived both treatments; neither treatment reduced the risk of pathogen dispersal. Concentrations of amino acids in the water were used as indicators of treatment-induced cell damage and demonstrated higher concentrations at discharge, but only after the EC treatments. Our results indicate that activity of bacteria, rather than their abundances, should be used when examining effects by ballast water treatment on microorganisms and that none of the examined treatment technologies could eliminate pathogenic bacteria.

A Screening Method for the Isolation of Bacteria Capable of Degrading Toxic Steroidal Glycoalkaloids Present in Potato.

Potato juice, a by-product of starch processing, is a potential high-value food ingredient due to its high protein content. However, conversion from feed to human protein requires the removal of the toxic antinutritional glycoalkaloids (GAs) α-chaconine and α-solanine. Detoxification by enzymatic removal could potentially provide an effective and environmentally friendly process for potato-derived food protein production. While degradation of GAs by microorganisms has been documented, there exists limited knowledge on the enzymes involved and in particular how bacteria degrade and metabolize GAs. Here we describe a series of methods for the isolation, screening, and selection of GA-degrading bacteria. Bacterial cultures from soils surrounding greened potatoes, including the potato peels, were established and select bacterial isolates were studied. Screening of bacterial crude extracts for the ability to hydrolyze GAs was performed using a combination of thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and liquid chromatography mass spectrometry (LC-MS). Analysis of the 16S rRNA sequences revealed that bacteria within the genus Arthrobacter were among the most efficient GA-degrading strains.

Conidia-based fluorescence quantification of Streptomyces.

Determination of cell numbers in filamentous bacteria, such as Streptomyces, is challenging due to the tangled and twisted structure of the filaments and formation of cell clumps in liquid cultures. Here, we developed a conidia-based approach, in which fluorescence of conidia, after staining with the DNA-binding stain SYBR Green 1, was related to SYBR Green 1 fluorescence of DNA in Streptomyces. When cell number in Streptomyces filaments, determined by the conidia assay, was compared to number obtained by a qPCR assay, 34 to 62% of cells in the Streptomyces filaments were recovered. The difference in numbers probably reflects an insufficient extraction of DNA from the Gram-positive bacteria, rather than underestimation of the actual cell number by the conidia-based determination. The conidia-based approach appears to be a fast and reliable procedure for counting cell numbers in Streptomyces filaments but it can also be used for other filamentous bacteria, if proper standard curves can be made.

Potential Contribution of Fish Feed and Phytoplankton to the Content of Volatile Terpenes in Cultured Pangasius (Pangasianodon hypophthalmus) and Tilapia (Oreochromis niloticus).

Geosmin and 2-methylisoborneol are the most recognized off-flavors in freshwater fish, but terpenes may also contribute off-flavor in fish. We identified six monoterpenes, 11 sesquiterpenes, and three terpene-related compounds in pangasius and tilapia from aquaculture farms in Bangladesh. The concentrations of most of the volatiles were below published odor thresholds, except for α-pinene, limonene, ß-caryophyllene, α-humulene, and ß-ionone in tilapia, and limonene and ß-ionone in pangasius. To identify sources of the terpenes, terpene profiles of fish feed and phytoplankton in the ponds were analyzed. In feed and mustard cake (feed ingredient), five monoterpenes and two sesquiterpenes were identified, and five of these compounds were also detected in the fish. In phytoplankton, 11 monoterpenes were found and three also occurred in the fish. The higher number of terpenes common to both fish and feed, than to fish and phytoplankton, suggests that feed was a more abundant source of odor-active terpenes in the fish than phytoplankton.

Predation and selection for antibiotic resistance in natural environments.

Genes encoding resistance to antibiotics appear, like the antibiotics themselves, to be ancient, originating long before the rise of the era of anthropogenic antibiotics. However, detailed understanding of the specific biological advantages of antibiotic resistance in natural environments is still lacking, thus limiting our efforts to prevent environmental influx of resistance genes. Here, we propose that antibiotic-resistant cells not only evade predation from antibiotic producers but also take advantage of nutrients released from cells that are killed by the antibiotic-producing bacteria. Thus, predation is potentially an important mechanism for driving antibiotic resistance during slow or stationary phase of growth when nutrients are deprived. This adds to explain the ancient nature and widespread occurrence of antibiotic resistance in natural environments unaffected by anthropogenic antibiotics. In particular, we suggest that nutrient-poor environments including indoor environments, for example, clean rooms and intensive care units may serve as a reservoir and source for antibiotic-producing as well as antibiotic-resistant bacteria.

The biosurfactant viscosin transiently stimulates n-hexadecane mineralization by a bacterial consortium.

Pseudomonas produces powerful lipopeptide biosurfactants including viscosin, massetolide A, putisolvin, and amphisin, but their ability to stimulate alkane mineralization and their utility for bioremediation have received limited attention. The four Pseudomonas lipopeptides yielded emulsification indices on hexadecane of 20-31% at 90 mg/l, which is comparable to values for the synthetic surfactant Tween 80. Viscosin was the optimal emulsifier and significantly stimulated n-hexadecane mineralization by diesel-degrading bacterial consortia but exclusively during the first 2 days of batch culture experiments. Growth of the consortia, as determined by OD600 measurements and quantification of the alkB marker gene for alkane degradation, was arrested after the first day of the experiment. In contrast, the control consortia continued to grow and reached higher OD600 values and higher alkB copy numbers during the next days. Due to the short-lived stimulation of n-hexadecane mineralization, the stability of viscosin was analyzed, and it was observed that added viscosin was degraded by the bacterial consortium during the first 2 days. Hence, viscosin has a potential as stimulator of alkane degradation, but its utility in bioremediation may be limited by its rapid degradation and growth-inhibiting properties.

Proteinase production in Pseudomonas fluorescens ON2 is affected by carbon sources and allows surface-attached but not planktonic cells to utilize protein for growth in lake water.

Proteins may be an important carbon and nitrogen source to bacteria in aquatic habitats, yet knowledge on the actual utilization of this substrate by proteolytic bacteria is scarce. In this study, Pseudomonas fluorescens ON2 produced an alkaline proteinase (AprX) during growth, and there was no evidence for cell density-regulated or starvation-induced proteinase production. Proteinase was produced in the absence of an organic nitrogen source, and citrate had a negative while glucose had a positive effect on the production. Hence, P. fluorescens ON2 seems to exploit protein sources by expressing the proteinase during growth unless a preferred carbon source such as citrate is present. Lake water model systems were subsequently used to investigate the ability of proteolytic vs. nonproteolytic ON2 strains to utilize protein for growth at moderate cell densities. Only cells forming surface-attached microcolonies were able to utilize this resource, while planktonic cells were not. Our experiments are the first to experimentally support models predicting that production of extracellular enzymes in dilute environments may be a waste of resources, whereas it represents a favorable feeding strategy in organic matrices such as detritus, microcolonies, or biofilm.

Chemical and sensory quantification of geosmin and 2-methylisoborneol in rainbow trout (Oncorhynchus mykiss) from recirculated aquacultures in relation to concentrations in basin water.

Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs.

Vogesella mureinivorans sp. nov., a peptidoglycan-degrading bacterium from lake water.

A novel, non-pigmented, rod-shaped, Gram-negative strain was isolated from mesotrophic lake water in Zealand, Denmark. Phylogenetic analysis of the 16S rRNA gene sequence of the bacterium, designated strain 389(T), indicated that the strain belonged to the genus Vogesella and formed a monophyletic group with Vogesella perlucida DS-28(T) (99.1 % nucleotide similarity); it was less related to Vogesella indigofera ATCC 19706(T) (96.9 % similarity) and Vogesella lacus LMG 24504(T) (96.8 % similarity). Hybridization of DNA from strain 389(T) and V. perlucida demonstrated a reassociation of 50.6 ± 9.6 %. The DNA G+C content of strain 389(T) was 61.2 mol%. The fatty acid profile of the strain differed from those of the other strains representing the genus Vogesella by a high content of C16:1ω7c and/or iso-C15:0 2-OH (71.6 %) and a lower content of C16: 0. Strain 389(T) was capable of degrading peptidoglycan and had chitinase and lysozyme activities, possibly associated with the degradation of peptidoglycan, and had capacity for degradation of several other polymer compounds. Based on phenotypic and genotypic characteristics, strain 389(T) represents a novel species, for which we propose the name Vogesella mureinivorans sp. nov. The type strain is 389(T) (=DSM 21247(T) =LMG 25302(T)).

Delftia lacustris sp. nov., a peptidoglycan-degrading bacterium from fresh water, and emended description of Delftia tsuruhatensis as a peptidoglycan-degrading bacterium.

Extracellular peptidoglycan is commonly found in natural environments, yet little is known about its biodegradation in nature. We here describe a novel peptidoglycan-degrading bacterium, designated strain 332T, isolated from mesotrophic lake water in Denmark. The strain was a Gram-negative-staining, motile rod. It had chitinase and lysozyme activities, which are relevant to peptidoglycan degradation, and was capable of utilizing several mono- and disaccharides, amino acids and organic acids. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain 332T belonged to the genus Delftia. Fatty acids of the strain included C8:0 and C10:0, which are characteristic of the genus Delftia. The DNA G+C content of the strain was 65.3 mol%. A DNA-DNA hybridization value of 66.2% was found between strain 332T and Delftia tsuruhatensis DSM 17581T. Based on differences in physiological and biochemical characteristics, the strain is considered to represent a novel species, for which the name Delftia lacustris sp. nov. is proposed. The type strain is 332T (=DSM 21246T=LMG 24775T). An emended description of Delftia tsuruhatensis is also presented.

Effect of availability of nitrogen compounds on community structure of aquatic bacteria in model systems.

To test if the quality and concentration of dissolved nitrogen (N) species could be a selective force in shaping bacterioplankton community structure, competition for various N compounds among five heterotrophic marine bacteria (Pseudomonas strains B, B25, and AX; Bacillus strain A6; Erythrobacter strain F19) was examined. Two of the five strains (AX and B25) were capable of utilizing urea for growth. The five strains were inoculated into dilute (1/1,000 strength) ZoBell medium enriched with various N sources (free amino acids, casein, ammonium, nitrate, or urea). Regardless of the added N source, the communities were either dominated by strain B (at 50 microM N) or strain AX (at 250 microM N). Without any addition of N, strain F19 dominated. If F19 was not included in the community, strain B25 dominated. Despite these differences in community structure, consumption of the added N compounds was surprisingly similar and no advantages of urea for the urea-utilizing bacterium B25 were obvious. To examine if urea could be of selective advantage to the urea-degrading strains B25 and AX, communities with and without B25 were amended with urea N. As expected, strain B25 became dominant when present, but without this strain the non-urea-utilizing strain B outcompeted the urea-utilizing strain AX. Possibly, strain B benefited from N released during catabolism of urea by strain AX. Changes in community composition did not result in major changes in the nitrogen dynamics. The results indicate that dissolved N species can be a selective force in shaping microbial communities. Relative to nutrient generalists, nutrient specialists may either have competitive advantages or stimulate growth of other species by synergetic interactions. Results from the model communities suggest that there may be a large degree of unpredictability in the making of microbial communities, whereas major ecosystem functions such as N cycling appear relatively stable.

Detection of activity among uncultured Actinobacteria in a drinking water reservoir.

The abundance, identity and activity of uncultured Bacteria and Actinobacteria present in a drinking water reservoir (North Pine Dam, Brisbane, Australia) were determined using a combination of fluorescence in situ hybridization (FISH) alone or with catalysed reporter deposition (CARD-FISH) with microautoradiography. The CARD-FISH technique was modified relative to previous described procedures and performed directly on gelatine cover slips in order to allow simultaneous combination with microautoradiography. Almost twofold higher numbers of microorganisms could be identified as either Bacteria or Actinobacteria using the CARD-FISH technique as compared with the traditional FISH technique. A combination of FISH or CARD-FISH with microautoradiography showed generally higher activity among the Actinobacteria than among all Bacteria. Another important observation was that many cells within the FISH-negative populations of both Actinobacteria and Bacteria were actively assimilating thymidine. Thus, great care should be taken when extrapolating the active fraction of a prokaryotic community to be equivalent to the FISH-detectable population in such environments. Bacterial groups within Actinobacteria produce the odours geosmin and 2-methylisoborneol, which lower the quality of surface water when used for drinking. The results indicate that combined microautoradiography and CARD-FISH may serve as an effective tool when studying identity and activity of microorganisms within freshwater environments.

Abundance of actinobacteria and production of geosmin and 2-methylisoborneol in Danish streams and fish ponds.

Occurrence of the odours geosmin and 2-methylisoborneol (MIB) in freshwater environments indicates that odour-producing organisms are commonly occurring. In the present study, we assumed actinomycetes to be a major source of the odours. Seasonal concentrations of odours and abundance of Actinobacteria, which includes actinomycetes and other G+ and high GC bacteria, were determined in one oligotrophic and two eutrophic freshwater streams, as well as in aquacultures connected to these streams, in Denmark. Concentrations of geosmin and MIB ranged from 2 to 9 ng l(-1) and were lowest in the winter. Passage of stream water in the aquacultures increased the amount of geosmin and MIB by up to 55% and 110%, respectively. Densities of actinobacteria were determined by fluorescence in situ hybridization with catalyzed reporter deposition (CARD-FISH) technique and were found to make up from 4 to 38 x 10(7) cells l(-1), corresponding to 3-9% of the total bacterial populations. The lowest densities of actinobacteria occurred in the winter. Filamentous bacteria targeted by the FISH probe made up about 2.7-38% (average was 22%) of the actinobacteria and were expected to be actinomycetes. Combined microautoradiography and CARD-FISH demonstrated that 10-38% (incorporation of 3H-thymidine) and 41-65% (incorporation of 3H-leucine) of the actinobacteria were metabolically active. The proportion of active actinobacteria increased up to 2-fold during passage of stream water in the aquacultures, and up to 98% of the cells became active. Sequencing of 16S rRNA genes in 8 bacterial isolates with typical actinomycete morphology from the streams and ponds demonstrated that most of them belonged to the genus Streptomyces. The isolated actinomycetes produced geosmin at rates from 0.1 to 35 aggeosmin bacterium(-1)h(-1). MIB was produced at similar rates in 5 isolates, whereas no MIB was produced by three of the isolates. Addition of the odours to stream water demonstrated that indigenous stream bacteria were capable of reducing the odours, and that enrichment with LB medium stimulated the degradation. Our study shows that bacterial communities in freshwater include geosmin- and MIB-producing actinobacteria. However, the mechanisms controlling production as well as degradation of the odours in natural waters appear complex and require further research.

Functional characteristics of culturable bacterioplankton from marine and estuarine environments.

Information on the structure of bacterioplankton communities is continuously increasing, while knowledge of their metabolic capabilities remains limited. In this study, the metabolic capacity of bacterioplankton was investigated, as such information is necessary to fully understand carbon cycling and other biogeochemical processes. The diversity of dominant culturable chemoorganotrophic bacteria from one estuarine and three marine environments was analyzed by random isolation of colony-forming units on solid media, taxonomical identification by partial 16S rRNA gene sequence analysis, and functional characterization of the isolates. A total of 76 16S rRNA gene sequences, representing 19 different genotypes, were obtained from the four sampling localities, including Bacillus, Pseudomonas, Pseudoalteromonas, Vibrio, and Erythrobacter as the most frequently isolated genera. The range of metabolic functions possessed by the cultured bacterial assemblages differed significantly between sites. Similarly, the percentage at each sampling station of bacteria capable of performing a specific function was significantly different for 18 of the 25 investigated metabolic functions. At two localities, the bacterial assemblages were dominated by a single genus (Pseudoalteromonas or Erythrobacter) and appeared to be functionally specialized. More than 95% of the isolates were capable of utilizing dissolved free amino acids and protein as their sole nitrogen sources, and all isolates of the specialized assemblages expressed beta-glucosidase. Furthermore, only some of the isolates were able to utilize NH4+, while up to two thirds of the isolates of the two marine sites were able to grow on NO3-.

Tenacibaculum skagerrakense sp. nov., a marine bacterium isolated from the pelagic zone in Skagerrak, Denmark.

A number of bacteria were isolated from sea water in Skagerrak, Denmark, at 30 m depth. Two of the isolates, strains D28 and D30(T), belonged to the Flavobacteriaceae within the Cytophaga-Flavobacterium-Bacteroides group. Sequencing of 16S rRNA genes of the two strains indicated strongly that they belonged to the genus Tenacibaculum and that they showed greatest similarity to the species Tenacibaculum amylolyticum and Tenacibaculum mesophilum. DNA-DNA hybridization values, DNA base composition and phenotypic characteristics separated the Skagerrak strains from the other species within TENACIBACULUM: Thus, it is concluded that the strains belong to a novel species within the genus Tenacibaculum, for which the name Tenacibaculum skagerrakense sp. nov. is proposed, with strain D30(T) (=ATCC BAA-458(T)=DSM 14836(T)) as the type strain.