Aburatsubo Inlet Research Articles

Draft Genome Sequence of Saccharospirillum sp. Strain MSK14-1, Isolated from Surface Seawater Collected at Aburatsubo Inlet in Japan.

ABSTRACTHere, we report the draft genome sequence of Saccharospirillum sp. strain MSK14-1, isolated from surface seawater collected at Aburatsubo Inlet in Japan. The genome sequence of strain MSK14-1 should contribute to our understanding of the characteristics of the genus Saccharospirillum.

Draft Genome Sequences of Two Fabibacter sp. Strains Isolated from Coastal Surface Water of Aburatsubo Inlet, Japan.

Here, we report the draft genome sequences of Fabibacter sp. strain 4D4 and F. misakiensis strain SK-8T, isolated from surface seawater of a semienclosed inlet.

Analysis of Nanoplankton Community Structure Using Flow Sorting and Molecular Techniques

We developed a method for the separate and simultaneous analysis of the community structure of heterotrophic nanopkankton (HNP) and autotrophic nanoplankton (ANP). This method consists of three steps. First, nanoplankton cells were concentrated using a cross-flow filtration system because cell densities in natural seawater are usually too low for genetic studies. Second, HNP and ANP were separated by flow cytometric sorting ("flow sorting") on the basis of the presence or absence of chlorophyll. Finally, the community structure was analyzed using denaturing gradient gel electrophoresis targeting 18S rRNA gene. The newly developed method was applied to the coastal surface water of Aburatsubo Inlet, Japan, in July 2008. The separation of nanoplankton into HNP and ANP was validated by phylogenetic analysis, and the trophic mode of uncultured nanoplankton was confirmed (e.g. Marine Alveolata group II [MALV II] and Marine Stramenopile clade-2 [MAST-2]). This new method involving cell concentration, flow sorting and phylogenetic analysis is a potentially powerful tool for evaluating the population dynamics and ecology of marine protozoa.

Tetrodotoxin in sinking particles from coastal waters

The occurrence of tetrodotoxin (TTX) in marine sinking particles was investigated. Sinking particles were collected in 1991 using sediment traps in the coastal area of Aburatsubo Inlet, Japan. TTX and related substances were analyzed by tissue culture bioassay, high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). TTX and related substances were detected from six samples. The concentrations were estimated to be ca. 200 to 1000 ng g-1 by the HPLC analyses. To our knowledge, this is the first report on the occurrence of TTX in particles in an aquatic environment. The present results indicate that sinking particles are one of the sources of TTX in the marine environment and that these particles play a role in the toxification of marine organisms.

Isolation and Characterization of a Chitin Degrading Marine Bacterium Belonging to the Genus Alteromonas.

A marine bacterium which produced an extracellular chitinase was isolated and identified. Out of 946 isolates from Aburatsubo Inlet, Sagami Bay and Otsuchi Bay, 95 were found to produce chitinases. We selected strain O-7 for further studies which was isolated from sediment sample at Sagami Bay at the depth of 5m, and showed a very high chitinase productivity. The strain O-7 was an aerobic, polarly flagellated, gram-negative, and rod-shaped organism with a low G+C contents (43.5mol%). The strain required seawater salts (0.8-7.0%) for the growth, indicating that this isolate is a marine strain. From the taxonomical characteristics, strain O-7 was identified as Alteromonas sp. Chitin was essential to produce chitinase as an inducer, and the optimum concentration of colloidal chitin for chitinase production was 0.5% (w/v).

Enumeration and characterization of nitrogen-fixing bacteria in an eelgrass (Zostera marina) bed

Marine nitrogen-fixing bacteria distributed in the eelgrass bed and seawater of Aburatsubo Inlet, Kanagawa, Japan were investigated using anaerobic and microaerobic enrichment culture methods. The present enrichment culture methods are simple and efficient for enumeration and isolation of nitrogen-fixing bacteria from marine environments. Mostprobable-number (MPN) values obtained for nitrogen-fixing bacteria ranged from 1.1×10(2) to 4.6×10(2)/ml for seawater, 4.0×10(4) to 4.3×10(5)/g wet wt for eelgrass-bed sediment, and 2.1 × 10(5) to 1.2 × 10(7)/g wet wt for eelgrass-root samples. More than 100 strains of halophilic, nitrogen-fixing bacteria belonging to the family Vibrionaceae were isolated from the MPN tubes. These isolates were roughly classified into seven groups on the basis of their physiological and biochemical characteristics. The majority of the isolates were assigned to the genusVibrio and one group to the genusPhotobacterium. However, there was also a group that could not be identified to the generic level. All isolates expressed nitrogen fixation activities under anaerobic conditions, and no organic growth factors were required for their activities.

New marine nitrogen-fixing bacteria isolated from an eelgrass (Zostera marina) bed

Four strains of marine nitrogen-fixing bacteria were isolated from the roots of eelgrass (Zostera marina) and from sediments in an eelgrass bed in Aburatsubo Inlet, Kanagawa Prefecture, Japan. Significant levels of nitrogenase activity were detected in all four strains after a few hours of incubation under anaerobic conditions. Nitrogenase activity in all cases was Na+ dependent. These strains grew anaerobically or under conditions of low oxygen, using molecular nitrogen as the sole nitrogen source. Bacterial growth in liquid nitrogen-free medium was accompanied by a marked pH decrease during the exponential growth phase. Neither yeast extract nor vitamins were required for the nitrogen fixation activity of these strains. Taxonomically, all strains were facultatively anaerobic, Gram-negative rods. They were motile in liquid medium by means of a single polar flagellum and required NaCl for their growth. These characteristics, as well as the guanine + cytosine content of their DNA (43.5 – 44.8 mol%), placed them in the family Vibrionaceae. These strains, however, could not be identified to the genus level because they were distinct from the two halophilic genera Vibrio and Photobacterium of the family Vibrionaceae by a variety of characteristics.

Nitrogen Fixation by Marine Agar-degrading Bacteria

Several strains of agar-degrading bacteria capable of fixing N2 were isolated from seawater and eelgrass-bed sediment in Aburatsubo Inlet, Kanagawa, Japan, during the summer of 1986. All strains were Gram-negative, facultatively anaerobic, and required NaCl for growth. They were straight or slightly curved rods and were motile in liquid medium by means of a single polar flagellum. These characteristics as well as the G+C contents of their DNA (44·7–46·1 mol%) placed them in the family Vibrionaceae. These strains produced extracellular agarase on agar medium, yielding reducing sugars and acids as the end products. They expressed significant nitrogenase (acetylene reduction) activities after a few hours of incubation under anaerobic conditions. They utilized combined nitrogen sources both aerobically and anaerobically, but fixed N2 only under anaerobic conditions. Neither yeast extract nor vitamins were required for N2 fixation. These strains were demonstrated to fix N2 anaerobically using agar as the sole carbon source.

Succession of Ciliated Protozoa on the Solid Surfaces of Substrata in Seawater

Change over a week period in the population composition of marine ciliates attached to solid substrata was studied. A number of 0.1mm thick Teflon and about 1mm thick microscopic glass slides were placed at depth of 0.5m in seawater at Aburatsubo Inlet, Kanagawa-ken. Heterotrophic nanoplankton (HNP), ciliated protozoa, algae and DAPI-stained bacterial cells were counted using Nomarsky and fluorescent microscope. A video camera attached to the microscope was used for identification of ciliates. The numbers of bacteria, HNP, and algal population on the substrata were much higher than those in the surrounding water. Ciliates (1200 and 2400 cells/cm2 on glass and Teflon slides, respectively) appeared on the first day and seemed to feed actively on attached microorganisms. Among the dominant ciliate population (Dysteria, Aspidisca, Geleia, Litonotus, Euplotes, Holosticha and Loxophyllum), bacteriovorous ciliates attached within the first 3 days to both substrata followed by the appearance of herbivorous species. Twenty three and seventeen species of ciliates were found on Teflon and glass slides, respectively. The maximum diversity index was observed on the fourth day on both substrata. Succession of ciliate species should be due to the change in food composition despite the nature of the substrata.

Isolation and characterization of marine bacteria producing alkaline protease inhibitor.

Marine bacteria which produced extracellular alkaline protease inhibitor were isolated and identified. A new and simple casein double layer agar method was employed for a quick screening of the inhibitor producers. Out of the 878 isolates from Aburatsubo Inlet, Kanagawa, Japan, only three strains produced the inhibitor whereas no inhibitor producer was found out of the 1, 961isolates from other sea areas. Among the three inhibitor producers, strain B-10-31 showed the largest inhibitory zone, suggesting that this strain had the strongest inhibitory activity.All the inhibitor producing strains were aerobic, polarly flagellated, Gram-negative, rodshaped organisms with low G+C contents in their DNAs (39.9 to 42.0mol%). They required NaCI for growth, which indicates that they are of marine origin. All the strains hydrolyzed complex polymers like casein, DNA, gelatin and starch. None of them utilized organic acids. Based on these taxonomical characteristics, they were identified as Alteromonas spp. Although the three strains belonged to the same genus, strain B-10-31 differed considerably in its characteristics from the other two (B-3-62 and B-3-87).This is the first report of a protease inhibitor producing bacteria isolated from seawater.

Distribution of Aerobic Bacteria Which Contain Bacteriochlorophyll a

Sixteen strains of aerobic bacteria which contain bacteriochlorophyll a were isolated from the samples collected in aerobic marine environments: thalli of Enteromorpha linza, Porphyra sp., Sargussum horneri; beach sand; and the surface seawater from Aburatsubo Inlet. When they occurred, their proportions among the aerobic heterotrophic populations ranged from 0.9 to 1.1% in the seaweed samples and from 1.2 to 6.3% in the beach sand samples and were 0.9% in the seawater sample. The results suggested that the aerobic photopigmented bacteria widely inhabit aerobic marine environments.

Occurrence and distribution of deoxyribonucleic acid-hydrolyzing bacteria in sea water

A large proportion of the heterotrophic bacteria isolated from sea water sampled from the Pacific Ocean and the neritic Sea of Japan were able to hydrolyze deoxyribonucleic acid (DNA). Their numbers ranged from 10 2 to 10 4 100 ml in the upper layers of the water profile and were less than 10 2 100 ml in deeper water in the open sea. In neritic regions, such as Aburatsubo Inlet, their numbers were higher, ranging between 10 5 and 10 7 100 ml . These organisms formed a constant proportion of the total heterotrophic bacterial populations and showed few seasonal fluctuations. In incubation experiments it was shown that the DNA occurring in sea water was extensively degraded in situ by the indigenous bacterial flora. More detailed examination of the degradation, using an isolated marine Vibrio sp., has demonstrated that purine and pyrimidine bases and inorganic orthophosphate are released into the medium. The bacterium totally assimilated the cytosine released and appeared to convert adenine to hypoxanthine. In contrast guanine and thymine attained constant concentrations in the medium.

Deoxyribonuclease activity in seawater and sediment

This paper describes a fluorometric method for assaying deoxyribonuclease (DNase) activity in natural seawater and sediment. DNase activity was detected in a sea-water sample taken from Tokyo Bay (Japan), and in various sediment samples taken from Suruga, Sagami and Tokyo Bays, and from Aburatsubo Inlet. Much more DNase occurred in seawater in a state bound to suspended particles or microbial cells than dissolved free in seawater. Although viable DNA-hydrolyzing bacteria were found to be widely distributed in seawater and sediment, poor correlation existed between the bacterial population and the intensity of DNase activity in the sediments examined. In addition, intensities of DNase activity in various surface sediments had no apparent correlation with the DNA contents and the sediment types. However, a close correspondence was found between the vertical variation of DNase activities and the gradient of DNA contents and of Eh in the core sediment at Aburatsubo Inlet.

Relation Between Production and Mineralization of Organic Matter in Aburatsubo Inlet, Japan

Studies carried out in Aburatsubo Inlet (35°09′N, 139°37′E) showed that generally during the spring the dark assimilation of carbon dioxide was a large fraction of the total carbon dioxide assimilated. During the rest of the year photosynthesis accounted for most of the production of the water column, but dark assimilation was sometimes appreciable in the sediments. Production generally exceeded mineralization, indicating a net gain of organic matter either in the sediments or in adjoining water masses.

油壷湾内における海洋性細菌の季節変動

油壷湾内における海洋性細菌の季節変動

Studies on Microbial Participation to Food Cycle in the Sea-II

The marine bacterium and protozoan, isolated at Aburatsubo Inlet in June, multiplied in the sea water with glucose and nitrate. The multiplication of the bacteria was not rapid in the solution, whereas the protozoa were considered to multiply rapidly in the solution after the logarithmic phase of the bacteria. As brine shrimp does grow little in the system with the nutrient of the bacteria and glucose, the cell substances of protozoan which utilized glucose and nitrate together with the bacterial cell substances are responsible for the growth of brine shrimp.