Microcultural study of bacterial size changes and microcolony and ultramicrocolony formation by heterotrophic bacteria in seawater

With a microculture technique and time-lapse, phase-contrast photomicrography, it was possible to follow the division of individual cells and the development of microcolonies of bacteria in freshly collected marine water samples. A certain number of marine bacteria, upon inoculation onto a nutrient rich agar surface, displayed an increase in size as well as a high growth rate. Other bacteria were identified as very small marine bacteria (ultramicrobacteria). These had a very slow growth rate when inoculated onto a nutrient-rich agar surface. These latter cells formed very small microcolonies (ultramicrocolonies), and cell size did not increase significantly. These two types of marine heterotrophs could be described in terms of zymogenous and autochthonous bacteria, a concept used by Winogradsky for describing soil microorganisms.

Dietary fructooligosaccharides and potential benefits on health

Fructooligosaccharides (FOS) are oligosaccharides that occur naturally in plants such as onion, chicory, garlic, asparagus, banana, artichoke, among many others. They are composed of linear chains of fructose units, linked by beta (2-1) bonds. The number of fructose units ranges from 2 to 60 and often terminate in a glucose unit. Dietary FOS are not hydrolyzed by small intestinal glycosidases and reach the cecum structurally unchanged. There, they are metabolized by the intestinal microflora to form short-chain carboxylic acids, L -lactate, CO(2), hydrogen and other metabolites. FOS have a number of interesting properties, including a low sweetness intensity; they are also calorie free, non-cariogenic and are considered as soluble dietary fibre. Furthermore, FOS have important beneficial physiological effects such as low carcinogenicity, a prebiotic effect, improved mineral absorption and decreased levels of serum cholesterol, triacylglycerols and phospholipids. Currently FOS are increasingly included in food products and infant formulas due to their prebiotic effect stimulate the growth of nonpathogenic intestinal microflora. Their consumption increases fecal bolus and the frequency of depositions, while a dose of 4-15 g/day given to healthy subjects will reduce constipation, considered one of the growing problems of modern society, and newborns during the first months of life.

Survival of indicators of bacterial and viral contamination in wastewater subjected to low temperatures and freezing: application to cold climate waste stabilisation ponds

The survival of bacterial and viral pollution indicators and Salmonella in urban wastewaters under freezing conditions (-14 degrees C for up to 60 days) is reported. Presumptive, total and faecal coliforms (PC, TC, FC), salmonellae and coliphages were tested. The dynamics of somatic coliphage (E. coli C) and F-pili specific coliphage inactivation were compared at 4 degrees C and 25 degrees C over various run times. On freezing of the wastewater, it was found that PC, TC and FC showed a first rapid phase (days) of inactivation followed by a slower second phase (up to 4 weeks) and then stabilisation at between 1-10% of the initial population size, depending on the wastewater sample used. Salmonella spp. were detectable in 0.1 ml of raw wastewater and were still detected up to 2 days after freezing but none were detected in 100 ml samples after 4, 42 and 60 days, although microbiologically similar but antigenically different forms were found. Viral indicators of pollution showed a slow but constant decrease in viability during the first month but then stabilised at between 10-20% survivors (10% in somatic E. coli C phages, 15.8% in somatic Salmonella phages and 17.9% in F-pili specific coliphages). Using electron microscopy, no difference in susceptibility to freezing could be detected with respect to morphological phage types, which were either small icosahedral particles or complex tailed phages. The study of viral indicators at 4 degrees C versus 25 degrees C showed a higher survival of the various coliphages over time at 4 degrees C. F-pili specific leviviridae were particularly susceptible to the antiviral factors at 25 degrees C and no viable units per ml were detected after one month at that temperature, whereas somatic coliphages were detected in higher numbers after this period, especially at 4 degrees C.

Ultrasonic ostectomy for the surgical approach of the maxillary sinus: a technical note

Because of its physical and mechanical properties, the odontologic applications of ultrasound are increasing. A new application of odontologic ultrasonic generators involves the lateral approach of the maxillary sinus in sinus augmentation. The procedure may provide important advantages over conventional ostectomy using diamond drills, as it reduces the risk of perforating the Schneiderian membrane, improves vision and hygiene of the operating area, and provides a more conservative and controlled osseous incision.

Formation of Stable Bdelloplasts as a Starvation-Survival Strategy of Marine Bdellovibrios

Several wild-type isolates of marine bdellovibrios formed stable bdelloplasts when they infected gram-negative bacterial prey under certain culture conditions. Synchronous predator-prey cultures and low nutrient concentrations increased the yield of stable bdelloplasts. The bdellovibrio cells retained in the stable bdelloplasts showed a high survival capacity in nutrient-depleted saline solution (10% viable Bdellovibrio cells after 3 months at 25°C), whereas Bdellovibrio attack-phase cells kept under the same starvation conditions lost viability more quickly (1% viable cells after 48 h). The addition of yeast extract to a stable bdelloplast suspension induced lysis of the bdelloplasts and release of motile infecting attack-phase Bdellovibrio cells. Other substances, such as free amino acids, protein hydrolysates, NH 4 + , carbohydrates, and organic amines, did not induce such a release. Stable bdelloplasts were highly hydrophobic and had a lower endogenous respiration rate than attack-phase cells. In general, stable bdelloplasts were almost as sensitive to temperature changes, desiccation, sonication, tannic acid, and Triton X-100 treatment as attack-phase cells. Electron microscopy of stable bdelloplasts did not reveal any extra cell wall layer, either in the bdelloplast envelope or in the retained Bdellovibrio cells, unlike the bdellocysts of the soil bacterium Bdellovibrio sp. strain W. We propose that formation of stable bdelloplasts is a survival strategy of marine bdellovibrios which occurs in response to nutrient- and prey-poor seawater habitats.

Isolation and characterization of marine and salt pond halophylic bdellovibrios

A method to enrich and isolate bdellovibrios from marine waters and solar salt evaporation ponds of a salinity up to 15.5% has been developed. The method promotes growth of gram-negative autochthonous bacteria followed by bdellovibrios that prey on them. Various Vibrio and Pseudomonas strains have been used to reveal Bdellovibrio plaques and in no case have bacteriophages interfered with the isolation technique. A total of 13 strains have been characterized by electron microscopy, host range, cytochrome spectra, and capacity to grow at different salt concentrations. All isolates show typical Bdellovibrio morphology and life cycle. Little differences could be found among the Bdellovibrio strains according to host range patterns with the exception of Bdellovibrio BS42 and BS43 that were unable to lyse various of the hosts used. These two Bdellovibrio strains differed too from the others in the cytochrome spectra of whole cell suspensions (α and β bands of the cytochrome c). All of the bdellovibrios isolated showed the typical bands of cytochromes a and c, and in some cases, the peak of cytochrome b could also be discerned. The Soret band has proved to be of great value to distinguish halophylic from freshwater bdellovibrios. The saline growth range found in this study is broader than the one described previously for marine bdellovibrios (1–6%). Some of the strains isolated from seawaters or from salt ponds could grow from 1 to 15% total salts salinity. The growth capacity at the highest salinities depends to a great extent on the proportion of salts in the medium. A compensated saline solution supports better Bdellovibrio proliferation than a solution where only the NaCl concentration has been increased. Tolerance to salinity divides the isolated bdellovibrios into two groups: a low salinity group of strains of marine origin able to grow at a salinity of 1% total salts, but not in freshwater media nor above 12% total salts, and a high salinity group isolated from solar evaporation ponds, with strains able to multiply in liquid media up to a salinity of 15% total salts, but unable to grow at a salinity of 1%. These results broaden the habitat of Bdellovibrio in saline waters of marine origin up to salinities of 15%, as well as indicate further diversity in this group of bacterial predators.Key words: halophylic Bdellovibrio, salterns, marine bacteria.

Evidence by electron micrographs for a high incidence of bacteriophage particles in the waters of Yaquina Bay, oregon: ecological and taxonomical implications

A variety of viral particles, the majority of them clearly identifiable as bacteriophages, were found in the seawater of Yaquina Bay, Oregon. These phages were obtained as free particles from the seawater without employing specific hosts for enrichments or further purification in the laboratory. A variety of electron micrographs showing different morphologies of phages as well as phage-bacterium interactions found in the seawater are presented. In the area where the bay received organic enrichment from seafood processing plants, a minimum of 10(4) phage particles per ml was estimated. Since the technique used was designed to concentrate particles 0.2 micrometer in diameter or larger it is assumed that the actual number of phage particles is higher than 10(4) particles per ml. The implications of the presence of such phage concentrations in bays and estuaries with a certain level of eutrophication are of obvious importance in considering the microbial ecology of these environments.

Further taxonomic characterization of the genus Bdellovibrio

Cultures of Bdellovibrio isolated from different geographic locations have been studied in terms of deoxyribonucleic acid analysis (% G + C, genome size, and DNA hybridization), cytochrome spectrum, and host range. Isolates of the genus exhibit a broad range of % G + C ranging from 37 to 51% and the genome sizes extend from 1300 x 10(6) to 1700 x 10(6) daltons. DNA hybridization continues to reveal a high level of genetic heterogeneity. Bdellovibrio 3294 exhibits 32% relative reassociation to Bdellovibrio W, 37% to Bdellovibrio stolpii Uki2, and an undetectible level to Bdellovibrio starrii A3.12 Bdellovibrio W is 23% related to B. starri A3.12 and 28.5% to B. stolpii Uki2. For the first time differential absorption techniques have revealed peaks of cytochrome b. The analysis of the cytochrome spectrum seems to be limited as a taxonomic tool since most of the recent isolates studied share a common cytochrome spectrum. Host-range studies have been found to be dependent on the experimental conditions, and with the exception of one isolate (B. starrii A3.12) the taxonomic significance of such techniques must be taken with caution.