Vibrio Ecology and Oil

For additional information:
Utilization of Hydrocarbons by Pathogenic Vibrios, Presentation to the South Central Branch – American Society for Microbiology Mississippi State University, October 27, 2012, D. Jay Grimes, et. al., PowerPoint presentation, pdf file

The Vibrio family of bacteria  includes the genera Vibrio and Photobacterium, both of which include species that are pathogenic for humans, fishes and marine invertebrates (shrimp, crabs, etc.). Having co-evolved with marine plants and animals millions of years ago, many Vibrios can live in and on marine life in a commensalistic (one species benefits) or mutualistic (both species benefit) manner.  But the bacteria can cause disease and even death when the marine host is weakened by injury, malnutrition, crowding such as occurs in aquaculture, or other stresses.

Vibrios are the dominant culturable marine bacteria.  While scientists have isolated and named more than 80 Vibrios,  most are fish pathogens and only 13 can cause disease in humans. However, it must be emphasized that scientists have only isolated and cultured fewer than 0.1% of the bacteria species thought to live in the oceans.

The Grimes lab is interested in the ecology of Vibrios including what traits allow the 13 species to colonize and cause disease in humans. One such factor, type III secretion systems (T3SS) in the human pathogen Vibrio parahaemolyticus, allows this species to inject proteins into its host.  This factor was the basis for a recent Ph.D. dissertation at GCRL (Noriea, 2012). Secretion systems are not unique to the Vibrios; many pathogenic bacteria possess T3SS-like systems that allow them to inject proteins (such as toxins) into their hosts. Vibrio cholerae
  Vibrio cholerae

Vibrio vulnificus an.d Vibrio parahaemolyticus (green colonies) and Vibrio cholerae (yellow colonies) growing in a culture medium Perhaps one of the most interesting aspects of the Vibrios is their ability to metabolize ("eat") a wide variety of materials including proteins, carbohydrates, fats, chitin (the material that forms marine invertebrate exoskeletons –  the second most abundant biopolymer on Earth after cellulose) and even petroleum. Many of the Vibrios can utilize petroleum compounds as their sole source of carbon and energy (food) and this feature is now being examined in the Grimes lab. Grimes and his students are investigating the ability of 48 strains, including V. cholerae, V. parahaemolyticus, V. vulnificus and Photobacterium damselae subspecies damselae, to metabolize petroleum, specifically oil recovered during the Deepwater Horizon top hat operation.  The  work is also considering naphthalene and phenanthrene; both are polycyclic aromatic hydrocarbons or PAHs  present in crude oil.
Vibrio vulnificus and Vibrio parahaemolyticus (green colonies) and Vibrio cholerae (yellow colonies) growing in a culture medium  

Data from the first trial revealed that all 48 strains of bacteria tested not only tolerated the oil, naphthalene, and phenanthrene, but were able to metabolize both the oil and these two PAHs. The experiment is now being repeated using a slightly different culture medium and we anticipate a third round of testing using yet a third culture medium. When complete, we anticipate that this work will provide two additional lines of evidence to support our findings in the first round of testing.

In addition, each strain of bacteria will be examined for the dioxygenase gene by extracting its DNA and polymerase chain amplifying the gene (if present) by using an appropriate dioxygenase DNA primer. Dioxygenases are required to break open (linearize) the aromatic rings that compose PAHs so that they can be metabolized with the Vibrio's tricarboxylic acid cycle or Krebs cycle. Bacteria lacking the dioxygenase may still be able to metabolize the less complex, non-aromatic crude oil molecules, but without the dioxygenase gene they are unable to metabolize PAHs.

Finally, Grimes is working with scientists at the J. Craig Venter Institute to identify bacteria and fungi associated with oiled Sargassum that was collected by GCRL fisheries biologist Jim Franks from an area near the DWH well in 2010 when it was still releasing petroleum. The JCVI scientists will use microbiomics procedures to extract DNA from oiled and control Sargassum so that bacteria and fungi present in the samples can be identified. Grimes will also examine the Sargassum with confocal laser scanning microscopy. The observations will determine whether bacteria and fungi are present on the Sargassum samples and whether they are in close proximity to the oil, which would further indicate that they were metabolizing the oil.

This research work is being conducted by GCRL without direct outside funding. A grant from the Northern Gulf Institute did fund the collection of samples being tested.

Dr. Jay Grimes and Hang Nguyen   Dr. Jay Grimes and Samantha “Sammy” Allen.
Dr. Jay Grimes and Hang Nguyen.
Hang was an NSF EPSCoR funded intern from
William Carey University.
  Dr. Jay Grimes and Samantha “Sammy” Allen.
Sammy was an NIH INBRE funded intern from Mississippi Gulf Coast Community College (MGCCC)