Biomedical subjects

A Kushmaro

Publications and source records attributed to A Kushmaro.

5 recordsLinked to original sources

PubMed2001

Vibrio shiloi sp. nov., the causative agent of bleaching of the coral Oculina patagonica.

The aetiological agent of bleaching of the coral Oculina patagonica was characterized as a new Vibrio species on the basis of 16S rDNA sequence, DNA-DNA hybridization data and phenotypic properties, including the cellular fatty acid profile. Based on its 16S rDNA and DNA-DNA hybridization, the new Vibrio species is closely related to Vibrio mediterranei. The name Vibrio shiloi sp. nov. is proposed for the new coral-bleaching species, the type strain being AK1T (= ATCC BAA-91T = DSM 13774T).

Animals↗

PubMed2000

Penetration of the coral-bleaching bacterium Vibrio shiloi into Oculina patagonica.

Inoculation of the coral-bleaching bacterium Vibrio shiloi into seawater containing its host Oculina patagonica led to adhesion of the bacteria to the coral surface via a beta-D-galactose receptor, followed by penetration of the bacteria into the coral tissue. The internalized V. shiloi cells were observed inside the exodermal layer of the coral by electron microscopy and fluorescence microscopy using specific anti-V. shiloi antibodies to stain the intracellular bacteria. At 29 degrees C, 80% of the bacteria bound to the coral within 8 h. Penetration, measured by the viable count (gentamicin invasion assay) inside the coral tissue, was 5.6, 20.9, and 21.7% of the initial inoculum at 8, 12, and 24 h, respectively. The viable count in the coral tissue decreased to 5.3% at 48 h, and none could be detected at 72 h. Determination of V. shiloi total counts (using the anti-V. shiloi antibodies) in the coral tissue showed results similar to viable counts for the first 12 h of infection. After 12 h, however, the total count more than doubled from 12 to 24 h and continued to rise, reaching a value 6 times that of the initial inoculum at 72 h. Thus, the intracellular V. shiloi organisms were transformed into a form that could multiply inside the coral tissue but did not form colonies on agar medium. Internalization of the bacteria was accompanied by the production of high concentrations of V. shiloi toxin P activity in the coral tissue. Internalization and multiplication of V. shiloi are discussed in terms of the mechanism of bacterial bleaching of corals.

Animals↗

PubMed1999

Inhibition of photosynthesis and bleaching of zooxanthellae by the coral pathogen Vibrio shiloi.

Vibrio shiloi is the causative agent of bleaching (loss of endosymbiotic zooxanthellae) of the coral Oculina patagonica in the Mediterranean Sea. To obtain information on the mechanism of bleaching, we examined the effect of secreted material (AK1-S) produced by V. shiloi on zooxanthellae isolated from corals. AK1-S caused a rapid inhibition of photosynthesis of the algae, as measured with a Mini-PAM fluorometer. The inhibition of photosynthesis was caused by (i) ammonia produced during the growth of V. shiloi on protein-containing media and (ii) a non-dialysable heat-resistant factor. This latter material did not inhibit photosynthesis of the algae by itself but, when added to different concentrations of NH4Cl, enhanced the inhibition approximately two- to threefold. Ammonia and the enhancer were effective to different degrees on zooxanthellae isolated from four species of coral examined. In addition to the rapid inhibition of photosynthesis, AK1-S caused bleaching (loss of pigmentation) and lysis of zooxanthellae. Bleaching was more rapid than lysis, reaching a peak (25% bleached algae) after 6 h. The factors in AK1-S responsible for bleaching and lysis were different from those responsible for the inhibition of photosynthesis, because they were heat sensitive, non-dialysable and active in the dark. Thus, the coral pathogen V. shiloi produces an array of extracellular materials that can inhibit photosynthesis, bleach and lyse zooxanthellae.

Ammonium Chloride↗

PubMed1998

Effect of Temperature on Adhesion of Vibrio Strain AK-1 to Oculina patagonica and on Coral Bleaching.

Laboratory aquarium experiments demonstrated that Vibrio strain AK-1 caused rapid and extensive bleaching of the coral Oculina patagonica at 29 degrees C, slower and less-complete bleaching at 23 degrees C, and no bleaching at 16 degrees C. At 29 degrees C, the application of approximately 100 Vibrio strain AK-1 cells directly onto the coral caused 50 and 83% bleaching after 10 and 20 days, respectively. At 16 degrees C, there was no bleaching, even with an initial inoculum of 1.2 x 10 bacteria. To begin to understand the effect of seawater temperature on bleaching of O. patagonica by Vibrio strain AK-1, adhesion of the bacteria to the coral as a function of temperature was studied. Inoculation of 10Vibrio strain AK-1 organisms into flasks containing 20 ml of seawater at 25 degrees C and a fragment of O. patagonica resulted in net levels of bacterial adhesion to the coral of 45, 78, and 84% after 2, 6, and 8 h, respectively. The adhesion was inhibited 65% by 0.001% d-galactose and 94% by 0.001% methyl-beta-d-galactopyranoside (beta-M-Gal). After the incubation of Vibrio strain AK-1 with the coral for 6 h, 42% of the input bacteria were released from the coral with 0.01% beta-M-Gal, compared to less than 0.2% when beta-M-Gal was present during the adhesion step. Adhesion did not occur when Vibrio strain AK-1 was grown at 16 degrees C, regardless of whether the corals were maintained at 16 or 25 degrees C, whereas bacteria grown at 25 degrees C adhered to corals maintained at 16 or 25 degrees C. Bacteria grown at 25 degrees C adhered avidly to Sepharose beads containing covalently bound beta-d-galactopyranoside but failed to bind if grown at 16 degrees C. These data suggest that elevated seawater temperatures may cause coral bleaching by allowing for the expression of adhesin genes of Vibrio strain AK-1.

Journal Article↗

PubMed1996

Oil bioremediation using insoluble nitrogen source.

Oil bioremediation is limited by the availability of nitrogen and phosphorous, which are needed by the bacteria and not present in sufficient amounts in hydrocarbons. The supply of these two essential elements as water-soluble salts presents several problems. These include the rapid dilution of the salts in the large volumes of polluted land or water and their utilization by other bacteria that do not degrade oil. In addition, increasing the concentration of mobile nitrogen creates further environmental problems. The use of hydrophobic sources of nitrogen and phosphorous that have a low water solubility can overcome these problems. We have studied one such compound. F-1, that is not used by most bacteria but serves as a good nitrogen and phosphorous source for those bacterial strains that are capable of utilizing it. We have shown that bacteria using F-1 do not cross-feed other bacterial strains. Moreover, when the concentration of the pollutant is sufficiently reduced, the multiplication of the bacteria slows down until they become a negligible fraction of the bacterial population. Chemical analysis indicated that following a 28-day treatment of Alaskan crude oil, most of the hydrocarbons, including polycyclic aromatics, are degraded to undetectable levels. The C34 and C35 components were also degraded, although their degradation was not completed within this time period. In treatment of a sandy beach that was accidentally polluted with crude heavy oil, about 90% degradation was obtained within about 4 months at an outside average temperature of 5 -10 degrees C.

Biodegradation, Environmental↗