James S. Maki

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.

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.

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.

Adhesion ofEnteromorpha swarmers to microbial films

Laboratory experiments were conducted to determine the effect of bacterial films on adhesion ofEnteromorpha sp. reproductive swarmer cells. Swarmers always attached in greater numbers to filmed than to unfilmed polystyrene surfaces. Surface energy measurements produced higher values on filmed surfaces than on unfilmed surfaces. Our data indicate that this higher surface energy may contribute to the increased adhesion by the algal swarmers.

Factors Influencing the Adhesion of Microorganisms to Surfaces

Abstract Starvation, growth phase, and carbon source influenced bacterial cell surface hydrophobicity. Both the number and kind of microorganisms that colonized metal surfaces depended on the type of metal and the presence of an imposed electrical potential. No significant differences in attachment and growth of a pure culture were observed when metal surfaces were dipped in an exogenous energy source. The chemical composition of naturally occurring adsorbed organic films on metal surfaces was shown to be independent of surface composition and polarization.

Involvement of Bacterial Exopolymers in Biodeterioration of Metals

Microbial degradation of metals is associated with a wide range of biochemical processes, including acid metabolite production, galvanic coupling and differential aeration cell formation, in all of which the role of bacterial exopolymers is crucial We obtained exopolymerfrom a number of pure cultures associated with metal surfaces and measured their binding characteristics with a number of metal ions (Fe, Cu, Mn, Ni). All of the exopolymers strongly bound the metals, but there was variation in maximum binding abilities and stability constants. Differential binding within the biofilm would result in preferential oxidation of particular metal species, eg. concentration of specific ions by the exopolymer of the biofilm may result in oxidation of less noble ions in the metal lattice. Using electrical and polarization resistance techniques the effect of exopolymer-producing bacteria on metal biodeterioration rates was studied. This report discusses the relationship between exopolymer binding and corrosion kinetics.

Biofilm formation on metal surfaces in antarctic waters

Foils of titanium and copper/nickel were exposed to Antarctic marine waters for periods of 15 min to 4 h during the Austral summer 1986. Some foils were exposed to subsurface water while others were inserted through the air/water interface prior to subsurface exposure. Pyrolysis/mass spectrometry was used to fingerprint surface bound organics. Attached bacteria were examined with epifluorescent and scanning electron microscopy. During the first 2 h copper/nickel accumulated significantly more pyrolysable organics than titanium. Differences in the surface bound organics on the two materials were not significant after 4 h. Throughout the exposure period higher numbers of bacteria were found attached to the titanium foils. Titanium foils that passed through the air/water interface prior to exposure showed a temporary increase in both pyrolysable organics and attached bacteria compared to identical foils exposed to subsurface waters. No significant increase in either parameter was observed on copper/nickel. O...

Biofilms and the survival of opportunistic pathogens in recycled water.

Microorganisms are likely to develop an organic film on pipes, water reservoirs and filters used for waste water reclamation during extended missions in space. These biofilms can serve to protect and concentrate potentially pathogenic microorganisms. Our investigation has emphasized the survival strategy of opportunistic pathogenic bacteria in distilled water. Pseudomonas aeruginosa and Staphylococcus aureus were used as test organisms. Cultures were incubated at 10 degrees, 25 degrees, and 37 degrees C. No viable Staphylococcus cells were detected after the first week of incubation. P. aeruginosa, however, survived in distilled water up to 5 months at all three temperatures tested. The starved cells were able to form a biofilm layer on stainless steel. The cells exhibited a negative surface charge. The charge may be involved in the adhesion of this bacterium to metal substrata. We are currently investigating the importance of adhesion in the survival of this and other potential human pathogens found in water recycling systems.

Mollicute identified in novel association with aquatic invertebrate

Prokaryotes lacking a cell wall, formerly known as mycoplasmas were recently designated as the new class, Mollicutes. The association of unidentified “mycoplasma-like organisms” with aquatic animals has been suggested previously on the basis of visual observations alone. We report the pure-culture identification of a true mollicute, anAcholeplasma, that consistently associates with the larvae and adults of the marine bryozoanWatersipora arcuata. This represents the first confirmed nondisease association between a mollicute and an aquatic invertebrate.

Survival of Pathogenic Bacteria Under Nutrient Starvation Conditions

The survival of opportunistic pathogenic microorganisms in water, under nutrient-limiting conditions, has been investigated in order to ascertain whether human pathogens can survive within a water-distribution system of the kind proposed for the NASA Space Station. Cultures of a strain of pseudomonas aeruginosa and two strains of staphylococcus aureus were incubated at 10, 25, or 37 C, and samples at 1 day, 1 week, 1 month, and six weeks. While neither of the staphylococcus strains tested were detected after 1 week of starvation, the pseudomonas strain can survive in deionized water at all three temperatures.