Vibrio vulnificus is an opportunistic marine pathogen that can cause fatal septicemic disease in both humans and eels (Gulig, Bourdage, & Starks, 2005;Morris, 1988). Human infections are generally associated with eating contaminated seafood or through open wounds that are exposed to contaminated seawater (Linkous & Oliver, 1999;Strom & Paranjpye, 2000). Fatal primary septicemia can progress rapidly, resulting in a mortality rate of >50% within days. In humans, V. vulnificus preferentially infects those who have pre-existing conditions associated with elevated iron levels, including cirrhosis, hemochromatosis, and thalassemia (Gulig et al., 2005).Vibrio vulnificus strains are divided into three biotypes: 1, 2, and 3. Biotypes 1 and 3 are known as opportunistic pathogens in humans while the Biotype 2 is primarily an eel pathogen, and only particular isolates have been implicated in human infection (

Solar water disinfection (SODIS) is a process by which microbially contaminated water is disinfected by transmitting solar ultraviolet radiation to the water, rendering the bacteria inactive. The purpose of this project was to determine a residence time for disinfection in specific applications using a 3-log reduction in colony-forming units per milliliter (CFU/mL). The water was contained in quartz tubes and tested over both flat and parabolic reflectors. While UVA and UVB radiation are diffuse and independent of reflector style, water temperature is affected by solar concentration. The two reflector styles were studied to identify how insolation level and temperature affects the bacteria inactivation process. Escherichia coli, DH5α, was inoculated into sterile water and treated for 2, 4, and 8 h. The study had several conclusions, first that a 5-log reduction was achieved after 2 h, for all water temperature and insolation levels. The reflector style did not have a measurable effect on inactivation due to the short disinfection time, but the water temperature increased significantly with the parabolic reflectors. A thermal model of the two systems confirmed that the parabolic configuration resulted in higher energy input, making it the preferred configuration for disinfection with lower residence times.

The Gram‐negative pathogen Vibrio vulnificus produces several iron‐sequestration systems including a hemin uptake system in response to iron limitation as a means to acquire this essential element. Strains of this organism are capable of causing serious septicemia in humans and eels, where hemin is abundant and an advantageous source of iron. Vibrio vulnificus hemin uptake systems consist of HupA, a well studied outer membrane protein, and a recently identified HvtA protein receptor. In this study, we confirmed that the expression of the hvtA gene is iron‐regulated in a fur‐dependent manner. When analyzed for virulence in a hemin‐overloaded murine model system, the hupA gene was more important for establishing infection than the hvtA gene. Transcriptional profiling of these genes using strains of two different biotypes, biotype 1 (human pathogen) and biotype 2 (eel pathogen), showed that the expression of the two receptors was also regulated in response to temperature. The expression of hupA was highly induced in elevated temperatures in the human pathogenic strain when tested in iron‐depleted conditions. Conversely, hvtA expression was induced significantly in the eel pathogenic strain at a lower temperature, a condition where the hupA locus was relatively repressed. Our results indicate that although both hupA and hvtA are involved for optimal hemin uptake in V. vulnificus, their expression is dually regulated by the environmental cues of iron concentration and temperature. Together, these data suggest that the virulence genes hupA and hvtA are tightly regulated and strictly induced during iron limitation combined with the physiological temperature of the host organism.

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