Nobuo Taga

Phosphatase activity and its rôle in the mineralization of organic phosphorus in coastal sea water

Abstract Alkaline phosphatase activity in sea-water samples taken from Tokyo, Sagami, and Suruga Bays in Japan was measured by a sensitive fluorometric method. There is a relationship between the phosphatase activity and bacterial biomasses in these three bays. The phosphatase-producing bacteria accounted for 40, 46, and 41% of heterotrophic bacteria in Tokyo, Sagami and Suruga Bays, respectively. Significant amounts of phosphatase-hydrolysable organic phosphorus were found in the euphotic zones of these bays and this organic phosphorus fraction accounted for 19 and 50% of organic phosphorus in Tokyo and Sagami Bays, respectively. Phosphatase-hydrolysable organic phosphorus was decomposed completely in the euphotic zone suggesting that this organic fraction is re-cycled in the primary production of the bays. Decomposition of natural organic phosphorus by enzymes was followed by measuring the release of inorganic orthophosphate from samples saturated with chloroform. Release of inorganic phosphorus proceeds rapidly for 2 or 3 days followed by a slow release. Enzymes present in the samples contributed to the decomposition of 50% of the organic phosphorus and the phosphatase enzyme was responsible for the decomposition of one-third of the hydrolysable organic phosphorus in the samples. Potential phosphatase activity in the samples was found to be indicative of the extent and rate of decomposition of organic phosphorus in coastal waters.

Heterotrophic bacteria attached to seaweeds

Abstract Viable counts of heterotrophic bacteria attached to the green algae, Monostroma nitidum Wittrock and Enteromorpha linza (Linne) J. Agardh, ranged from 10 4 to 10 6 /cm 2 , and those attached to the red alga Porphyra suborbiculata Kjellman from 10 3 to 10 4 /cm 2 . These bacterial populations were larger than those attached to the brown alga Eisenia bicyclis (Kjellman) setchell ranging from 10 1 to 10 4 /cm 2 . The bacterial populations in the environmental sea water. Nabem Inlet and Otsuchi Bay (Japan), were 10 3 /ml. Orange and yellow pigmented bacteria were predominant on the green and red algae, but not in the bacterial populations of the brown alga and the sea water. Most of the pigmented bacteria were identified as belonging to the Flavobacterium-Cytophaga group. A beneficial relationship was suggested between the green algae and the pigmented bacteria. Proportions of Vibrionaceae were small on the green algae.

Effect of Skeletonema costatum (Grev.) Cleve on the growth of marine bacteria

Abstract The effect of Skeletonema costatum (Grev.) Cleve on bacterial growth was investigated in mixed culture. Twenty marine bacterial strains of four genera were tested. Generally, the growth of Pseudomonas and Vibrio was inhibited by the alga. Conversely, the growth of Flavobacterium was apparently stimulated. A clear tendency was not obtained for Acinetobacter . The inhibitory action of Skeletonema costatum was strongest during the exponential growth phase under 3,000 lux illumination. Further enrichment with nitrogen and phosphorus sources and glucose as a carbon source had no influence on the action, but yeast extract counteracted it. Only slight suppression of bacterial growth was shown by an algal culture filtrate.

Microbiological studies of Tokyo Bay

The generic composition of the heterotrophic bacterial population of Tokyo Bay, which is now highly polluted and eutrophic, was compared with that of the adjacent, less polluted regions of Sagami Bay and Suruga Bay. Members of Vibrionaceae predominated in the bacterial flora of seawater and zooplankton samples from Sagami Bay, Suruga Bay, and the mouth of Tokyo Bay. However,Vibrio spp. formed only a small proportion of the bacterial population of the water and sediment samples from the inner Tokyo Bay; there the Gram-negative, nonmotile, nonpigmented bacteria, which were tentatively identified asAcinetobacter, were predominant. The result of experiments, in which seawater samples from Tokyo Bay were incubated under various experimental conditions, indicated that two significant factors apparently control the growth ofVibrio spp. in seawater; (1) a direct antagonism betweenVibrios and phytoplankton undergoing rapid growth, and (2) a limiting organic nutrient forvibrios.

Bacterial attachment to phytoplankton in sea water

Abstract Bacterial attachment to phytoplankton cells was investigated in natural sea water and with a mixed culture of Flavobacterium T-8D and marine diatom, Skeletonema costatum (Grev.) Cleve. The attached bacteria on incubated natural phytoplankton cells were considerably different from those in the surrounding sea water. The attachment rate of T-8D to the alga depended on the algal growth phase and light, but not on the bacterial concentration. The attachment of this strain to glass surfaces depended on the bacterial concentration. The results indicate that characteristic bacterial groups will attach to phytoplankton cells depending on the physiological condition of the algae, but not on the concentration of bacteria or dissolved organic matter.

Fluctuation of the communities of heterotrophic bacteria during the decomposition process of phytoplankton

Abstract The fluctuations of the number and the communities of heterotrophic bacteria were investigated during the decomposition processes of two marine phytoplanktons, Chlorella sp. and Skeletonema costatum (Grev.) Cleve, under laboratory conditions. The concentration of particulate organic carbon (POC) decreased rapidly during the first 5 days. The number of the heterotrophic bacteria increased rapidly on the first day, the maximum value of plate counts was obtained on the 5th day. During the decomposition of phytoplankton, the communities of bacteria attached to particulate organic matter (POM) were quite different from that of free-living bacteria in the surrounding sea water. The dominant communities of heterotrophic bacteria attached to POM changed not only from Pseudomonas-Alcaligenes group to Acinetobacter-Moraxella group, but also from the communities with high potential ability to decompose high molecular organic substrates to one with low ability, suggesting that there is a succession of bacterial communities involved in the decomposition of POM.

Distribution of Nitrogen-fixing Bacteria in the Central Pacific Ocean*

The plate culture method using the two formulae for non-nitrogenous media was adopted in this investigation for the purpose of counting and isolating nitrogen-fixing bacteria distributed in the open sea.Sea water samples were collected at eighteen different stations in the region of Lat. 50°N–15°S along Long. 155°W and two other stations in the Pacific Ocean. In order to compare with those samples from the open sea, water samples were also obtained at four stations in Suruga and Sagami Bays.Nitrogen-fixing bacteria appear to be widely but very unevenly distributed at all depths in sea water, in numbers approximately ranging from nil to 104 per 100 ml of sea water, and denser vertical populations have been found in the area of Lat. 40°N and 5°N along Long. 155°W, even at depths from 2,000 to 3,000m. A conparatively denser population of bacteria was found in sea water from Suruga Bay and Sagami Bay.The bacteria associated with plankton were abundantly demonstrated, in numbers ranging from 106 to 108 per 1 ml settling volume of plankton, in many plankton samples collected at four stations in the southern parts of the Pacific Ocean. Almost all the bacteria isolated from the samples of blue green algal colonies,Trichodesmium, sp., were able to grow on nonnitrogeneous media.

Distribution and seasonal variation of vitamin B12, thiamine and biotin in the sea

Abstract The distributions and seasonal variations of vitamin B 12 , thiamine and biotin were investigated in waters of the North Pacific Ocean, the East China Sea, and the bays and inlets along the Pacific coast of Japan, by use of microbiological assay methods. A marine diatom Cyclotella nana clone 3H for vitamin B 12 , and marine yeast Cryptococcus albidus for thiamine, and a marine bacterium Achromobacter sp. strain yH-51 for biotin were used as assay organisms. In the surface water of Sagami Bay, monthly changes in the amounts of the three dissolved vitamins followed closely that of chlorophyll a , being highest in July and lowest during late autumn and winter. The geographical and vertical distributions of thiamine and biotin in the sea generally showed similar patterns to that of chlorophyll a , whereas vitamin B 12 did not always follow the trend. Amounts of particulate thiamine and biotin corresponded to about 1 % of that of the dissolved form in the surface water of the North Pacific Ocean. In the coastal waters, however, they were at times found to be 144.0 % and 53.9 % respectively.

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

Abstract 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 102 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 105 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.

Occurrence and distribution of phosphatase in neritic and oceanic sediments

Abstract A fluorometric method using 3-o-methylfluorescein phosphate as a substrate was used to determine phosphatase in marine sediments. Alkaline phosphatase was detected in all sediments from both neritic and oceanic regions of the Pacific Ocean, Sulu Sea, Timor Sea, Sahul Shelf, and South China Sea. Significant activity was found even in sediments from depths of 5900 to 7700 m. Phosphatase activity was generally highest at the surface of the sediments and decreased with increasing depth; in the surface layers it tended to decrease as the depth of overlying water increased. There was a positive relationship between the phosphatase activity and the total and inorganic phosphorus contents.