Filterable marine bacteria found in the deep sea: Distribution, taxonomy, and response to starvation

Abstract

A significant number of viable colony-forming bacteria were recovered from deep-ocean bottom water samples passed through a 0.45μm filter. However, these bacteria small enough to pass through a 0.45μm membrane filter and termed "filterable bacteria" were less abundant in open-ocean surface water and coastal water samples. The reduced size of bacterial cells present in deep-ocean bottom water samples was documented by scanning electron microscopy. The concentration of ATP in the water samples was found to be correlated with results of direct counts of bacteria.Numerical taxonomy of bacterial strains isolated from water samples collected at two stations in the deep sea yielded taxonomic clusters grouped according to sample and size fraction. The generic composition of bacterial populations of bottom water filtrates was compared with that of bacteria retained by 0.45μ m filters. Strains ofAlcaligenes, Flavobacterium, Pseudomonas, andVibrio spp. were identified among those retained by, as well as passing through, 0.45μm filters.Two marine isolates obtained from the filtrate of a deep-ocean water sample were incubated for 9 weeks in nutrient-free artificial seawater, during which the cells became rounded and reduced in size. After the 9-week incubation period, more than 10% of the viable cells of both cultures were able to pass through a 0.4μm filter. The viable count at 9 weeks wasca. 10% of that of the initial population, although from direct counts the total population number remained relatively constant throughout the incubation period. From the observed reduction in cell size and increased starvation resistance of cells held under low nutrient conditions, it is concluded that a significant relationship exists between decreased cell size and increased survival of marine bacteria in the deep sea.

Sphingomonas alaskensis sp. nov., a dominant bacterium from a marine oligotrophic environment.

“…It is often assumed that the strikingly small size ( 0n1 µm$) of the bacterial cells of marine bacterioplankton communities (Amy & Morita, 1983 ;Hood & MacDonell, 1987 ;Lee & Fuhrman, 1987 ;MacDonell & Hood, 1982 ;Morita, 1997 ;Tabor et al, 1981) is due to the fact that they represent starved forms of known and unknown bacteria. However, it has gradually become apparent that these so-called ' ultramicrobacteria ' (Torella & Morita, 1981) are mostly metabolically active and growing (Button & Robertson, 1989 ;Cho & Azam, 1988 ;Ishida & Kadota, 1981 ;Kaprelyants et al, 1993 ;Kirchman, 1993 ;Schut et al, 1993Schut et al, , 1997a.…”

Distribution and molecular weight of dissolved DNA in subtropical estuarine and oceanic environments

“…Subsurface maximums in chlorophyll a values may occur as a result of the density structure of the water column or as a result of behavioral and growth responses to light and nutrient levels (Cullen & Eppley 1981). Bacteria capable of passing 0.2 gm filters ('filterable bacteria' or 'ultramicrobacteria') have been described in estuarine and marine environments (Tabor et al 1981, Torrella & Morita 1981, MacDonnell & Hood 1982. It is possible that these organisms contribute to the dissolved DNA signal.…”

Deep-sea hydrothermal vent bacteria related to human pathogenic Vibrio species

“…Barotolerant Vibrio spp. have been isolated from deep-sea sediment and from the gut microflora of invertebrates and fish collected from a variety of deepsea habitats, including hydrothermal vents (16,17). For example, strains of Vibrio, Aeromonas, and Pseudomonas spp.…”

“…Several culturedependent and -independent studies have confirmed the ubiquity of vibrios, and suggested Vibrio populations generally comprise approximately 1% (by molecular techniques) of the total bacterioplankton in estuaries (19), in contrast to culture-based studies demonstrating that vibrios can comprise up to 10% of culturable marine bacteria (20). Clearly, vibrios are ubiquitous and abundant in the aquatic environment on a global scale, including both seawater and sediment (19,(21)(22)(23)(24)(25), and repeatedly shown to be present in high densities in and on marine organisms, such as corals (26), fish (27-29), mollusks (30), seagrass, sponges, shrimp (28, 31), and zooplankton (16,17,28,32,33).During dives of the deep-sea submersibles Alvin and Nautile in 1999 along the East Pacific Rise, southwest of the Mexico coast, samples of water surrounding sulfide chimneys of a hydrothermal vent community were collected and four mesophilic bacterial isolates were cultured, which were subsequently tested for phenotypic traits, including growth on V. cholerae selective thiosulfate-citrate-bile-salts-sucrose (TCBS) agar (Oxoid). The sampling locations from where these four mesophilic bacteria were isolated are described in Table 1.…”

“…Several culturedependent and -independent studies have confirmed the ubiquity of vibrios, and suggested Vibrio populations generally comprise approximately 1% (by molecular techniques) of the total bacterioplankton in estuaries (19), in contrast to culture-based studies demonstrating that vibrios can comprise up to 10% of culturable marine bacteria (20). Clearly, vibrios are ubiquitous and abundant in the aquatic environment on a global scale, including both seawater and sediment (19,(21)(22)(23)(24)(25), and repeatedly shown to be present in high densities in and on marine organisms, such as corals (26), fish (27-29), mollusks (30), seagrass, sponges, shrimp (28, 31), and zooplankton (16,17,28,32,33).…”