Correlation between Possession of a Respiration-Dependent Na Pump and Na Requirement for Growth of Marine Bacteria

The possession of a respiration-dependent primary sodium pump and the requirement of Na for growth were investigated in bacterial isolates from marine environments. The bacteria in which NADH oxidase specifically required Na for maximum activity were believed to possess a primary sodium pump. All bacteria that failed to grow without the addition of NaCl possessed a primary Na pump. All bacteria that had no primary Na pump grew without additional NaCl. The primary Na pump seems to be involved in the Na requirement of marine bacteria, and this can be regarded as a criterion for the definition of marine bacteria.     

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.     

A method of the selective isolation and enumeration of marine Vibrionaceae

A noninhibitory medium and GasPack anaerobic culture system were employed for the selective enumeration and isolation of Vibrionaceae in seawater and marine sediments.Vibrio counts obtained by the new method for seawater and sediment samples were compared with vibrio numbers in the heterotrophic bacterial population appearing on a medium routinely employed in the laboratory for such counts. The ratio of the former to the latter counts ranged from 0.5 to 1.3, the average being 0.96. The seawater and sediment bacteria that grew and produced visible colonies on the medium under anaerobic conditions for 3 days at 20°C were almost exclusively vibrios.From the results reported here it is concluded that most of the vibrios present in seawater and sediment samples can be recovered by the new method developed in this study.     

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.     

Phylogeographic insights into the invasion history and secondary spread of the signal crayfish in Japan

Successful invasion by nonindigenous species is often attributed to high propagule pressure, yet some foreign species become widespread despite showing reduced genetic variation due to founder effects. The signal crayfish (Pacifastacus leniusculus) is one such example, where rapid spread across Japan in recent decades is believed to be the result of only three founding populations. To infer the history and explore the success of this remarkable crayfish invasion, we combined detailed phylogeographical and morphological analyses conducted in both the introduced and native ranges. We sequenced 16S mitochondrial DNA of signal crayfish from across the introduced range in Japan (537 samples, 20 sites) and the native range in western North America (700 samples, 50 sites). Because chela size is often related to aggressive behavior in crayfish, and hence, their invasion success, we also measured chela size of a subset of specimens in both introduced and native ranges. Genetic diversity of introduced signal crayfish populations was as high as that of the dominant phylogeographic group in the native range, suggesting high propagule pressure during invasion. More recently established crayfish populations in Japan that originated through secondary spread from one of the founding populations exhibit reduced genetic diversity relative to older populations, probably as a result of founder effects. However, these newer populations also show larger chela size, consistent with expectations of rapid adaptations or phenotypic responses during the invasion process. Introduced signal crayfish populations in Japan originate from multiple source populations from a wide geographic range in the native range of western North America. A combination of high genetic diversity, especially for older populations in the invasive range, and rapid adaptation to colonization, manifested as larger chela in recent invasions, likely contribute to invasion success of signal crayfish in Japan.     

Shoreline urbanization interrupts allochthonous subsidies to a benthic consumer over a gradient of lake size

The role of resource subsidies across ecosystem boundaries has emerged as an important concept in contemporary ecology. For lake ecosystems, this has led to interest in quantifying the contribution of terrestrial allochthonous carbon to aquatic secondary production. An inverse relationship between habitat area and the role of allochthonous subsidies has been documented on marine islands and assumed for lakes, yet there have been no tests of this pattern among benthic (lake bottom) consumers. Here, we used carbon stable isotopes to trace terrestrial allochthonous and benthic autochthonous carbon use by the crayfish Pacifastacus leniusculus over a gradient of lake area, productivity and urbanization. Consistent with findings from terrestrial islands, habitat size dictated the importance of allochthonous subsidies, as P. leniusculus transitioned from using predominantly terrestrial carbon in small lakes to an increased reliance on autochthonous production in larger lakes. However, shoreline urbanization interacted with this pattern, particularly for small lakes where greater urbanization resulted in reduced use of allochthonous resources. As such, we provide, to our knowledge, the first confirmation of the predicted relationship between habitat size and importance of allochthonous subsidies to lake benthic consumers, but found that urbanization can interfere with this pattern.     

Habitat Segregation and Biochemical Activities of Marine Members of the Family Vibrionaceae

A comparative study of marine members of the family Vibrionaceae with the technique of numerical taxonomy revealed habitat segregation as well as a cosmopolitan nature of species distribution among the vibrios in different marine environments. The bacterial strains analyzed were isolated from seawater, sediments, phyto- and zooplankton, and fish in the Indian Ocean, the South and East China Sea, and West Pacific Ocean, and coastal areas of Japan. A total of 155 morphological, physiological, and biochemical tests were carried out for each of 405 strains examined. The results showed that most of the large taxonomical clusters which emerged from the computation corresponded to ecological groups which have particular niches. For instance, each group of seawater vibrios inhabited a particular water layer of limited depth range, in spite of the fact that strains of the group were isolated from sampling locations spread over a wide area from the Indian Ocean to Japanese coast. Various vibrio groups showed remarkable differences in their physiological and biochemical activities, and the activities of each group seemed to correspond with its ecological niche. The strains which inhabited surface-water layers grew fast and actively utilized many high-molecular-weight organic compounds and carbohydrates that are derived from fresh, easily degradable organic matter present in the surface waters, whereas the middle- and deep-water vibrios did not decompose most of the high-molecular-weight organic compounds except chitin but, rather, utilized some carbohydrates and organic acids which seemed to be derived from refractory particulate organic matter present in the deeper waters.     

Taxonomy of four marine bacterial strains that produce tetrodotoxin

Four strains of tetrodotoxin-producing bacteria isolated from a red alga and from pufferfish were characterized. Two of these strains are members of the genus Listonella MacDonell and Colwell. The phenotypic characteristics, guanine-plus-cytosine contents, and base sequences of the 16S rRNAs of these organisms indicated that they are members of Listonella pelagia (Vibrio pelagius) biovar II. The other two strains are members of the genus Alteromonas Baumann et al. and the genus Shewanella MacDonell and Colwell. These two strains are mutually distinct and distinct from the previously described Alteromonas and Shewanella species and therefore are placed in new species. The names Shewanella alga and Alteromonas tetraodonis are proposed for these organisms; the type strains are strains OK-1 and GFC, respectively.     

Distribution and significance of heterotrophic marine bacteria with antibacterial activity

Bacteria with antibacterial activity were isolated from seawater, sediments, phytoplankton, and zooplankton of Suruga, Sagami, and Tokyo Bays and from soft corals and sponges collected from the Taiwan coast. Of the 726 strains isolated, 37 showed antibacterial activity against either Vibrio parahaemolyticus (ATCC 17802) or Staphylococcus aureus (P209). Sediment harbored the lowest number of these forms of bacteria, and those from Tokyo Bay did not show any activity. Attached isolates showed greater activity compared with free-living forms. Relatively high numbers of strains with antibacterial activity were associated with phytoplankton. Among the zooplankton isolates, cladocerans harbored the maximum number of antibacterial strains. Isolates were more inhibitory to gram-positive test cultures. Autoinhibition was observed only among 8% of the isolates. Marine nonproducers were more susceptible. Pseudomonas/Alteromonas species made up 81.0% of isolates, of which 30% were pigmented strains. The absence or reduction in number of bacteria with antibacterial activity in Tokyo Bay is attributed to its eutrophic nature, which may tend to moderate the production of antibacterial compounds.