Continuous culture with deep seawater of a benthic food diatom Nitzschia sp.

A continuous culture system for a benthic food diatom Nitzschia sp. wasestablished by using properties of high nutrient and clean of deep seawater(DSW). DSW collected from 320 m depth in Muroto City, Japan, was introducedinto a glass-pipe bioreactor (14 cm length, 3 cm diam.) containing glassbeads of 0.5 cm diam. as substrata for the alga, and it was incubated at18°C · 80Em^–2sec^–1 · L:D=14:10. The chlorophyll a yield of benthicdiatoms in a reactor as a unit of surface area of the substratum was only0.001–0.003 g cm^–2 when the flow rate of DSW was 0(batch culture conditions). However, when DSW was supplied continuously to areactor, the yield increased to 1.4 g-chl.a cm^–2 alongwith the increase in flow rate of DSW. Moreover, amounts of chl.a washed outof the system were negligible, 0.0014 to 0.0045%, even though theflow rate of DSW was as much as 25 times h^–1, suggesting thatsloughing of benthic diatoms from the substratum was minimized. Although theyield of diatoms fluctuated significantly at the time that the DSW wascollected, the variation could be minimized by increasing the flow rate ofDSW. These results indicate that the continuous culturing system with DSWsupports the stable and effective mass culture of benthic food diatom.     

洞头海区大型海藻养殖净化海水水质的研究

调查了2008年浙江温州洞头海区大型经济海藻羊栖莱和坛紫菜的养殖面积和产量,实验室内测定了藻体内的总氮（TN）、总磷（TP）含量,估算出大型海藻养殖从洞头海区除去N约196t,P近10t。海藻养殖有效净化了洞头海区海水水质、降低了赤潮发生频率。     

Changes in culture and biochemical characteristics of Salmonella paratyphi B after incubation in seawater]

After incubation in seawater Salmonella paratyphi B cells rapidly became unable to grow on bacteriological media. Previous adaptation to high osmolarity conditions greatly slowed down this process. Strains isolated from seawater microcosms after varying incubation periods were qualitatively different and showed changes in some of their growth (colony shape and size) and biochemical properties (acidification of some sugars, gelatinase activity, acetoin production, nitrate reduction). Because of these modifications, the bacteria showed atypical profiles and could not be identified as members of the Salmonella genus. The alteration of the phenotype, although reversible, could explain some of the false-negative results obtained upon isolation and identification of these bacteria in seawater samples.     

Diversity and distribution of epibiotic bacteria on Pseudo-nitzschia multiseries (Bacillariophyceae) in culture, and comparison with those on diatoms in native seawater

Previous studies on the interaction between bacteria and harmful algal bloom species have mostly considered the bacteria in the bulk solution. Here, we document the abundance and mode of attachment of bacteria growing on the cell surface of the domoic acid-producing diatom Pseudo-nitzschia multiseries (Hasle) Hasle in culture, compared with diatoms in field samples. The epiphytic bacteria were examined by scanning electron microscopy to visualize their morphology and mode of attachment. Two P. multiseries cultures were studied: clone CLN-1 and sub-clone CLN-1-NRC; the latter had been maintained in another laboratory for 2 years. Each of these P. multiseries cultures exhibited a clearly different assemblage of epibiotic bacteria, even though both originated from the same parent culture. The bacterial diversity was greater in clone CLN-1 (nine distinct morphotypes seen) than in sub-clone CLN-1-NRC (six morphotypes). The former clone also produced more domoic acid than the latter. There was a succession of bacterial morphotypes as well as an increase in the number of epiphytic bacteria per diatom cell during the progression from exponential to stationary phase. The most diverse and common morphotypes were rod-shaped cells (e.g. a Caulobacter-like bacterium attached by a discoid holdfast). Epibionts showed a preference for attachment at specific regions of the host diatom frustule, e.g. the raphe or cingulum, locations where organic matter may be extruding from the diatom cell. Most diatom cells carried only one to five bacteria, and up to ca. 60% of the intact diatom cells (although intact cells themselves were infrequent) were still free of epibiotic bacteria at the end of the 31-day batch culture experiment. Sequencing of the SSU rRNA gene showed that five of the eight bacterial strains isolated from the P. multiseries cultures were members of the Alphaproteobacteria, three of the Gammaproteobacteria and one of the Bacteroidetes. A morphologically diverse assemblage of epibiotic bacteria was also found on both centric and pennate planktonic diatoms in natural coastal waters. Of the eight morphotypes recorded, all but two were also found in the cultures. Relatively fewer wild diatom cells carried bacteria compared to cells in culture. We hypothesize that the diversity and abundance of epiphytic bacteria may explain some of the variability seen in the production of DA by different P. multiseries clones, and should be considered as another important and controllable variable that influences diatom cell physiology.     

Nature of Escherichia coli cell lysis by culture supernatants of Bacillus species

Escherichia coli cells were found to be sensitive to lysis by the supernatants of a variety of protease-positive Bacillus species when treated at 45 degrees C but not when treated at 37 degrees C. Different E. coli strains manifested different lysis sensitivities when treated at 45 degrees C. When the lysis rates of E. coli cells at various stages of growth were investigated, post-exponential-phase cells were shown to be most sensitive to lysis. The lysis rate was inversely related to cell viability, and susceptibility appeared to be at least partly due to lysis of dead E. coli cells. A close relation was observed between levels of lysis activity and proteolytic activity. A Bacillus subtilis mutant lacking alkaline and neutral protease activity failed to lyse E. coli cells. It was concluded that Bacillus proteases played a major role in the observed E. coli lysis.     

The degradation of Karenia brevis toxins utilizing ozonated seawater

Florida red tides impose both an economic and health impact on the state. The purpose of this research was to examine the effectiveness of ozone to reduce the numbers of Florida red tide organism (Karenia brevis Davis) and its associated toxins in an artificial seawater environment. The results obtained in this experiment showed an approximate 1.25 log₁₀ unit reduction in the major toxin groups recovered after 10 min of ozone exposure (approximately 135 mg). In initial trials, K. brevis toxins were extracted and reintroduced into an artificial seawater (ASW) media. Subsequent experiments exposed whole cell K. brevis culture to ozone treatment. Samples from both experiments displayed approximately 1.10 log₁₀ unit reduction in total toxin and an approximate 1.25 log₁₀ unit reduction in three of the six major toxins associated with K. brevis (PxTx-1, -2, -9). The reduction in toxin concentration, as measured by high performance liquid chromatography (HPLC) analysis, displayed a positive correlation with the reduction of toxicity as determined by a fish (Cyprinodon variegatus) bioassay. Despite large total doses of ozone applied, as compared to levels that might be found at a commercial ozonation facility, some toxins were still recoverable by HPLC after ozone treatment.     

Growth and production of Thai agarophyte cultured in natural pond using the effluent seawater from shrimp culture

Hydrobiologia - Growth rate determinations of the Thai agarophytes, Gracilaria fisheri (Xia et Abbott) Abbott, Zhang et Xia and G. tenuistipitata Chang et Xia var. liui Chang et Xia, were conducted...     

Nature of Escherichia coli cell lysis by culture supernatants of Bacillus species.

Escherichia coli cells were found to be sensitive to lysis by the supernatants of a variety of protease-positive Bacillus species when treated at 45 degrees C but not when treated at 37 degrees C. Different E. coli strains manifested different lysis sensitivities when treated at 45 degrees C. When the lysis rates of E. coli cells at various stages of growth were investigated, post-exponential-phase cells were shown to be most sensitive to lysis. The lysis rate was inversely related to cell viability, and susceptibility appeared to be at least partly due to lysis of dead E. coli cells. A close relation was observed between levels of lysis activity and proteolytic activity. A Bacillus subtilis mutant lacking alkaline and neutral protease activity failed to lyse E. coli cells. It was concluded that Bacillus proteases played a major role in the observed E. coli lysis.     

Survival of the North American strain of viral hemorrhagic septicemia virus (VHSV) in filtered seawater and seawater containing ovarian fluid, crude oil and serum-enriched culture medium

The North American strain of viral hemorrhagic septicemia virus (NA-VHSV) could be recovered for up to 40 h in natural filtered seawater (27 ppt) with a 50% loss of infectivity after approximately 10 h at 15 degrees C. Addition of 10 ppb North Slope crude oil to the seawater had no effect on virus survival. However, when various concentrations of teleost ovarian fluid were added to seawater, virus could be recovered after 72 h at 0.01% ovarian fluid and after 96 h at 1.0%. When cell culture medium supplemented with 10% fetal bovine serum was added to the seawater, 100% of the virus could be recovered for the first 15 d and 60% of the virus remained after 36 d. These findings quantify NA-VHSV infectivity in natural seawater and demonstrate that ovarian fluid, which occurs naturally during spawning events, significantly prolongs the survival and infectivity of the virus. The extended stabilization of virus in culture medium supplemented with serum allows for low titer field samples to be collected and transported in an unfrozen state without significant loss of virus titer.     

Nature of the phenotypic variability of somatic cells in culture: unstable phenotypic changes

It was stated elsewhere ( Glebov , Abramyan , 1983) that the appearance of a number of phenotypic variants detected in somatic cell populations with high frequency should be provided by genetical unstable alterations. The properties of somatic cell variants that reproduce unstably a changable phenotype in the course of cell generations are analysed. These variants: (1) appear accidentally and independently on selectivity agent; (2) as a rule, the frequency of the variant arising does not increase under the action of mutagens; (3) the phenotypic reversion of unstable variants is a stochastic process; (4) such variants are characterized by intraclonal heterogeneity and by the segregation of stable alternative variants. The number of properties of phenotypically unstable variants isolated by one-step selection is similar to those for somatic cell variants isolated in the course of multistep selection. The latter are characterized by phenotypic reversion too. The appearance of unstable phenotypic variants is concluded to be associated with the genetical unstable alterations. It is argued that at least part of above alterations should be induced by the insertion of mobile genetic elements. The features of karyotypical variation in somatic cell population allow to conclude that the karyotype of cultured somatic cells is a genetically unstable attribute. The features mentioned above are: a high frequency of karyotypical alterations which is inherited by the cells with difference in the frequency of arising of karyotypical alteratons . The unstability of karyotype is restricted to the genetic unstability that is seen from non-random karyotypic variation, and interclonal difference in the chromosome stability. The site-specificity of karyotype alterations that proceed with high frequency allow to put forward a hypothesis that the process of mobile genetic element transposition is induced on the early stages of the history of constant cultured cell lines.     

Influence of seawater Sr content on coral Sr/Ca and Sr thermometry

The Ca content of a Porites coral from Xisha, South China Sea is quite uniform along its 18-year growth axis. A comparison with previously published data shows that the Ca content of corals from different sites varies by only 0.4%. This is much smaller than the variation of Ca in seawater (2.2%), indicating that Ca variations in seawater do not significantly affect the Ca compositions of coral skeletons. The variation in skeletal Ca contents results in only ±0.6°C of uncertainty in SST calculations, which is much smaller than the large disparities observed for previously established coral Sr/Ca thermometers. In contrast, Sr in tropical seawater varies spatially by as much as 2.4%, corresponding to ~4°C offset for coral Sr/Ca calibrations. The effect of seawater Sr variations on coral Sr/Ca thermometers is evaluated and we demonstrate that the content of seawater Sr is the major factor responsible for disparities in these coral Sr/Ca thermometers. The disparities can be significantly reduced when seawater Sr contents are included in the Sr/Ca thermometers.     

Home occupancy by male Octopus vulgaris in a large seawater tank

Pairs of individually recognizable male Octopus vulgaris were observed in a large seawater tank containing two suitable homes (brick pots or plastic buckets). None of the animals established exclusive occupancy of one home and for much of the time both animals were associated together at the same site. Usually one of the two homes was preferred and its occupant was most likely to be the larger animal, or the earlier resident if they were of equal size. Large animals were observed to take food forcefully from smaller octopus. An arm alignment interaction is described which, it is suggested, may be a means by which two octopuses establish their relative sizes.