Hydrothermal impacts on trace element and isotope ocean biogeochemistry.

Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Impacts of atmospheric anthropogenic nitrogen on the open ocean.

Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.

Broad spectrum antimicrobial activity of a new multi-purpose disinfecting solution.

PURPOSE: There has been increasing awareness of the need for more powerful contact lens disinfectants, ideally having low toxicity and allergenicity to ocular tissue. Opti-Free Express with ALDOX Multi-Purpose Disinfecting Solution (MPDS) was recently marketed as a new multi-purpose disinfecting solution for soft contact lenses. MPDS contains two antimicrobial agents, polyquaternium-1 and myristamidopropyl dimethylamine, to broaden the range of antimicrobial activity. The purpose of this study was to evaluate the antimicrobial activity of MPDS against microorganisms that have been reported as contact lens and lens case contaminants and causative agents of microbial keratitis. METHODS: MPDS was challenged with high numbers of gram-positive and gram-negative bacteria, yeast, mold, and Acanthamoeba. Several lots of product were challenged with at least three separate inocula of each isolate. After exposure to the disinfecting solution, a sample was removed from the product and plated for survivors by suitable recovery methods. The plates were incubated and the number of survivors was enumerated. RESULTS: The results showed that MPDS was bactericidal, fungicidal and amoebicidal against an extensive variety of environmental contaminants of lens care accessories and ocular pathogens. MPDS was capable of killing a broad spectrum of microorganisms. The log reduction exceeded the primary criteria for disinfecting products and produced a notable reduction of other clinical and environmental isolates as well. CONCLUSIONS: Opti-Free Express MPDS contains antimicrobial agents that can kill an extensive spectrum of many different types of microorganisms that may contaminate contact lenses and solutions.

Loss of bactericidal activity from contact lens storage solutions.

PURPOSE: The purpose of this study was to evaluate the effect of lens storage on the bactericidal activities of disinfecting solutions. METHODS: HYDROCURVEII (55% water content) soft contact lenses were soaked in OPTI-FREE Rinsing, Disinfecting, and Storage Solution (preserved with polyquaternium-1 [PQ-1]) or ReNu Multi-Purpose Solution (polyaminopropyl biguanide [PHMB]). After the lenses were removed, solutions were challenged with Pseudomonas aeruginosa and Staphylococcus aureus. Uptake of the antimicrobial agents by the lenses was evaluated by placing the lenses on plates seeded with S. aureus and observing for zones of growth inhibition. RESULTS: The bactericidal activity of the PHMB preserved solution decreased after 4 hours of storage time and showed no activity after storage for 3 days. Lenses soaked in the PHMB preserved solution produced zones of inhibition. The results suggest that the PHMB in the solution accumulates in the lens. This decreases the levels of preservative in the solution that is no longer available during lens storage. Neither decrease in bactericidal activity nor accumulation of the PQ-1 preservative in the lens occurred during storage with the PQ-1 solution. CONCLUSION: These results demonstrate that PQ-1 preserved solutions maintain bactericidal activity overnight and during prolonged storage without detectable uptake by lenses.

Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions.

The wetting and soaking solutions and contact lens cases of eye clinic patients commonly were contaminated with gram-negative bacteria during their use. Serratia marcescens occurred most frequently in preserved solutions, whereas Pseudomonas aeruginosa was most often recovered from home-prepared saline. The bacteria were recovered at densities of greater than 10(6) cells per ml and typically persisted in the solutions. Eight patients who developed bacterial keratitis during 1986 used solutions contaminated with the etiological agents of the infections. Improper hygienic practices of the patients and failure of some preservative systems were implicated in the development of the infections.

Antibiograms, serotypes, and plasmid profiles of Pseudomonas aeruginosa associated with corneal ulcers and contact lens wear.

Pseudomonas aeruginosa was isolated from the corneal scrapings of 11 of 14 patients with gram-negative corneal ulcers and from salt tablet-prepared saline solutions from 6 of these patients wearing soft contact lenses. Comparison of physiological properties, antibiograms, serotypes, and plasmid profiles for five of the patients indicated that the isolates from the ulcer and the saline solution of a given patients were of the same strain. Improper hygienic practices of contact lens wearers appeared to be a major factor in the epidemiology of pseudomonad corneal ulcers.

Characterization of atypical Candida tropicalis and other uncommon clinical yeast isolates.

Clinical yeast isolates representing alpha-glucoside-deficient variants of Candida tropicalis, C. lusitaniae, atypical C. albicans, and Saccharomyces cerevisiae were characterized. Additional physiological tests, including cellobiose fermentation, rhamnose assimilation, and triphenyl tetrazolium chloride reduction, are recommended for the detection and presumptive identification of uncommon Candida spp. in the clinical laboratory.

Pseudomonas corneal ulcers associated with soft contact-lens wear.

Seven Pseudomonas corneal ulcers in six patients were associated with soft contact-lens wear and use of saline solutions prepared from distilled water and sodium chloride tablets. The same species of Pseudomonas isolated from the corneal ulcers were also isolated from the home-prepared saline and in one instance from the water used to prepare the saline solution. In three of the six patients, the pseudomonad isolated from the corneal ulcer was of the same serotype and biochemically identical to the pseudomonad from the patients' saline solution. Commercially available distilled water, even brands recommended for use with soft contact lenses, was found to be contaminated with gram-negative bacteria before use. Clinical histories disclosed that all patients inappropriately used the home-prepared saline as a wetting agent, or eyedrop, or bath, after thermal disinfection of the contact lens. Self-inoculation of the eye with contaminated saline is a hazard for soft contact-lens wearers who use home-prepared saline solution.

Primary acute histoplasmosis in guinea pigs exposed to aerosolized Histoplasma capsulatum.

Guinea pigs were examined as a possible in vivo model for human histoplasmosis. Guinea pigs were exposed to an aerosol of viable microconidia and mycelial fragments of Histoplasma capsulatum generated in a Henderson apparatus. Colonization and infection of the lungs occurred, with subsequent involvement of the regional lymph nodes and reticuloendothelial organs. Cultural recovery of the fungus from the nasopharynx and bronchoalveoli was initially high, but decreased with time. The mean number of colonies recovered from the lungs gradually increased, reaching a peak at 2 weeks, with involvement of the regional lymph nodes. Extrathoracic dissemination to the liver and spleen occurred in only a few animals. After 4 weeks, all tissues except the cervical and tracheobronchial lymph nodes were culturally negative; all specimens were culturally negative after 8 weeks. Disappearance of H. capsulatum from tissues appeared to correlate inversely with the development of hypersensitivity as measured by skin test reactivity. Histopathological studies supported cultural results and were similar to those described for primary human and canine histoplasmosis.

Isolation of Candida albicans from freshwater and sewage.

The isolation and identification of Candida albicans from polluted aquatic environments were facilitated by the inclusion of a selective medium and a differential screening medium to detect the reduction of 2,3,5-triphenyltetrazolium chloride. C. albicans occurred commonly in low numbers in sewage influents, rivers, and streams.

Genital herpesvirus hominis infection in mice. I. Development of an experimental model.

Pregnant female mice, after intravaginal inoculation with Herpesvirus hominis (HVH) type 2, developed vaginitis on days 5 to 7 after virus challenge, followed by hunching and hind limb paralysis on days 7 to 9 and death from encephalitis on days 9 to 11. After initial replication in the mucous membranes of the genital tract, virus spread to the spinal cord and ascended to involve the brain. Viremia or replication of H. hominis type 2 in the liver or spleen was not detected. Virus was cleared from vaginal secretions by days 8 to 10 after infection. Pregnant mice were more susceptible to the infection than nonpregnant mice. This experimental infection in female mice provides a model for genital herpesvirus infection and for herpesvirus infection and for herpesvirus encephalitis in which one can evaluate potentially promising antiviral chemotherapeutic agents.