Ralph Mitchell

Inhibition of attachment of larval barnacles, Balanus amphitrite, by bacterial surface films

Films of bacteria on solid substrata can positively or negatively influence the attachment of marine invertebrate larvae. Effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite Darwin were examined in the laboratory. Bacteria, grown to mid-exponential phase and allowed to adsorb irreversibly to polystyrene petri dishes, attached in densities of 107 cells cm-2. Assays (22h) were used to compare the effects of adsorbed cells of 18 different bacterial species on larval barnacle attachment. Most of the adsorbed bacteria either inhibited or had no effect on larval attachment compared to clean surfaces. Experiments testing the effect of larval age on barnacle attachment were conducted with six species of bacteria and showed that older larvae attached in higher percentages to clean surfaces and that bacterial films generally inhibited larval attaschment. Both the species of bacteria and the in situ age of the adsorbed bacteria affected barnacle attachment response: older films of Deleya (Pseudomonas) marina were more inhibitory. Bacterial extracellular materials may be involved in the inhibitory process.

Biodeterioration of concrete by the fungus Fusarium

The bacterial genus Thiobacillus is known for its ability to degrade concrete. A fungus was isolated from concrete samples and identified as a Fusarium species. Our data indicate that fungi also play an important role in the deterioration of concrete. We observed both weight loss and release of calcium when concrete was exposed to our isolate. Fungal degradation proceeded more rapidly than Thiobacillus-mediated degradation. Our study suggests that interaction between fungal metabolites and calcium in the concrete results in the formation of soluble calcium organic complexes.

Bacteria induce settlement and metamorphosis of Janua (Dexiospira) brasiliensis Grube (Polychaeta:Spirprbidae)

Abstract Larvae of the spirorbid Janua (Dexiospira) brasiliensis Grube settle on multi-species microbial films grown in laboratory aquaria. Bacteria appear to be responsible for inducing metamorphosis. Larvae of Janua rarely settled on films of the diatom Nitzchia . The larvae settled on pure culture films of bacteria isolated from the green macroalga Ulva lobata , a common natural substratum for Janua (Dexiospira) brasiliensis . Individual bacterial strains varied in their capacity to induce settlement and metamorphosis. Our data suggest that the metamorphic cue is associated with the surface of selected bacterial species.

Inhibition of larval barnacle attachment to bacterial films: An investigation of physical properties.

The effects of films of two strains of a marine bacterium, Deleya marina (ATCC 25374 and 27129) on the attachment response of cypris larvae of the balanomorph barnacle, Balanus amphitrite, were examined in the laboratory. Tests showed that the cell-surface hydrophobicities of the two bacteria in suspension were different. In contrast, films derived from these cells were both highly wettable (i.e., displayed high surface free energy). Assays (22 hours) compared permanent attachment of larval barnacles to films derived from exponential and stationary phase cells for both bacteria. These films either had no effect or inhibited attachment of both 0-day- and 4-day-old cypris larvae when compared with unfilmed controls. Our data indicate that inhibition of larval barnacle attachment by films of the two bacteria is the result of factors other than surface free energy. Production of chemical barnacle settlement inhibitors by the bacteria is hypothesized.

The Ecology of Microbial Corrosion

Corrosion reactions may be induced or enhanced by microbial activity. The classic corrosion reaction is electrochemical, resulting in the dissolution of metal from anodic sites with subsequent electron acceptance at cathodic sites. Consumption of electrons varies, depending on the redox potential of the surface. In an aerobic environment, oxygen is the electron acceptor, forming metal oxides and hydroxides. At low redox potentials, protons become the electron acceptors, yielding hydrogen gas and other highly reduced products. The process of corrosion is accelerated by removal of the end products of the chemical reactions.

Characterization of a new thermophilic sulfate-reducing bacterium

A thermophilic sulfate-reducing vibrio isolated from thermal vent water in Yellowstone Lake, Wyoming, USA is described. The gram-negative, curved rod-shaped cells averaged 0.3 μm wide and 1.5 μm long. They were motile by means of a single polar flagellum. Growth was observed between 40° and 70 °C with optimal growth at 65 °C. Cultures remained viable for one year at 27 °C although spore-formation was not observed. Sulfate, thiosulfate and sulfite were used as electron acceptors. Sulfur, fumarate and nitrate were not reduced. In the presence of sulfate, growth was observed only with lactate, pyruvate, hydrogen plus acetate, or formate plus acetate. Pyruvate was the only compound observed to support fermentative growth. Pyruvate and lactate were oxidized to acetate. Desulfofuscidin and c-type cytochromes were present. The G+C content was 29.5 mol%. The divergence in the 16S ribosomal RNA sequences between the new isolate and Thermodesulfobacterium commune suggests that these two thermophilic sulfate-reducing bacteria represent different genera. These two bacteria depict a lineage that branches deeply within the Bacteria domain and which is clearly distinct from previously defined phylogenetic lines of sulfate-reducing bacteria. Strain YP87 is described as the type strain of the new genus and species Thermodesulfovibrio yellowstonii. Yellowstone Lake (Wyoming, USA) is located within one of the most tectonically active regions in the world (Klump et al. 1988; Remsen et al. 1990). Hydrothermal springs, hot gas fumaroles and elevated substrata temperatures have been observed within the lake itself (e.g., Remsen et al. 1990). Hydrothermal vent waters were reported to be anoxic, high in dissolved nutrients relative to the lake water and to have temperatures in excess of 80 °C (Klump et al. 1988; Remsen et al. 1990). Sulfate concentrations averaged 380 μM in vent waters and 80 μM in bulk lake water (Klump et al. 1988; Remsen et al. 1990). On the basis of on these physical and chemical characteristics, and the observation (e.g., Zeikus et al. 1983) that microbial sulfate reduction is prevalent in the thermal aquatic environments of Yellowstone National Park, we hypothesized that hydrothermal vent waters in Yellowstone Lake could support the growth of thermophilic sulfate reducers.Here we describe the general characteristics of a new thermophilic sulfate reducing bacterium, Thermodesulfovibrio yellowstonii, which was isolated from hydrothermal vent water in Sedge Bay of Yellowstone Lake, Wyoming, USA. In addition, we report on the phylogenetic relationship of this new isolate with other thermophilic and mesophilic sulfate-reducing bacteria.

Ion and neuropharmacological studies of barnacle settlement

Abstract Experiments tested effects of altering ion concentrations and the effects of additions of biologically active substances in the media surrounding settling stage barnacle larvae. Alteration of ionic concentrations did not result in induction of metamorphosis. Excess potassium ion, magnesium ion and calcium ion inhibited settlement. Potassium ion affected young cyprids while other cations had more pronounced effects on older cyprids. Replacement of one cation by another reduced the inhibitory effects of all but calcium. Excess magnesium was routinely inhibitory while lowered magnesium had little effect. Calcium ion could be increased 50% by lowering magnesium concentrations without affecting settlement. However, low calcium ion concentrations inhibited settlement. Of the biologically active substances tested, only soluble barnacle settlement factor and dibuteryl cAMP induced metamorphosis. SITS, a calcium channel blocker, inhibited settlement and negated the effects SF +. Most of the other compounds inhibited settlement at millimolar concentrations and had no effect when tested at lower concentrations. Picrotoxin, a compound that interferes with chloride ion movement (and membrane depolarization) strongly inhibited metamorphosis with an EC50 of 10−6 mol.

The role of microbial biofilms in deterioration of space station candidate materials

Formation of microbial biofilms on surfaces of a wide range of materials being considered as candidates for use on the International Space Station was investigated. The materials included a fibre-reinforced polymeric composite, an adhesive sealant, a polyimide insulation foam, teflon cable insulation, titanium, and an aliphatic polyurethane coating. They were exposed to a natural mixed population of bacteria under controlled conditions of temperature and relative humidity (RH). Biofilms formed on the surfaces of the materials at a wide range of temperatures and RHs. The biofilm population was dominated by Pseudomonas aeruginosa, Ochrobactrum anthropi, Alcaligenes denitrificans, Xanthomonas maltophila, and Vibrio harveyi. The biocide, diiodomethyl-p-tolyl sulfone, impregnated in the polyurethane coating, was ineffective against microbial colonization and growth. Degradation of the polyurethane coatings was monitored with electrochemical impedance spectroscopy (EIS). The impedance spectra indicated that microbial degradation of the coating occurred in several stages. The initial decreases in impedance were due to the transport of water and solutes into the polymeric matrices. Further decreases were a result of polymer degradation by microorganisms. Our data showed that these candidate materials for space application are susceptible to biofilm formation and subsequent degradation. Our study suggests that candidate materials for use in space missions need to be carefully evaluated for their susceptibility to microbial biofilm formation and biodegradation.

Processes controlling virus inactivation in coastal waters

Abstract The mechanisms controlling virus inactivation in coastal waters are discussed. Chemical and biological processes appear to be important but a purely thermal mechanism is probably not significant. Viral association with colloidal and particulate materials prolong survival and may enhance the transport of viruses to marine sediments. Sewage management practices are evaluated for efficiency in the control of viral contamination of bathing and shellfishing waters.

Effect of colloids on the survival of bacteriophages in seawater

Abstract A study was undertaken on the effect of colloids on the survival of bacteriophage T 7 in natural seawater. It was found that the biological inactivation of virus T 7 was controlled by the addition of inorganic and organic colloids. Colloidal montmorillonite and Escherichia coli K cells protected the virus from inactivation in natural seawater. The nature of this protective effect is discussed.