Whole genome sequencing of Moraxella bovis identifies two major genotypes
Researchers in the USA have revealed that there are two different genotypes of Moraxella bovis, a bacterium that causes infectious bovine keratoconjunctivitis (IBK, also known as ‘pinkeye’), an economically significant and painful eye disease that affects cattle worldwide. The findings, published in BMC Microbiology, will help researchers understand how different types of M. bovis cause infection in livestock and can help develop preventative measures to protect cattle against this disease.
USDA Agricultural Research Service (ARS) and University of Nebraska-Lincoln (UNL) scientists sequenced and compared the genomes of a collection of M. bovis variants and found that they consisted of two major genotypes that differ in both chromosome content and plasmid profiles and may not equally associate with IBK.
“We found major differences in virulence factors between the two genotypes,” said Emily Wynn, ARS research microbiologist. “For example, M. bovis has a toxin, called hemolysin toxin, which it uses to penetrate the eye. We found that the two genotypes have different versions of the toxin. This difference and others among the collection of M. bovis variants could mean that there are variations in their ability to cause disease.”
In addition, the scientists identified outer membrane proteins that could potentially be used as a target to develop specific preventative actions against select or all genotypes of M. bovis.
This is important because for years scientists have been closely looking at pilin proteins in this bacterium to develop interventions against the disease. Pilins facilitate the attachment of M. bovis to the eye. However, using pilins to develop interventions could be difficult.
“The pilin gene of M. bovis can undergo an inversion,” said Mike Clawson, ARS research molecular biologist. “This is where parts of the gene flip and are rearranged on the bacterial chromosome. As a result, a newly formed pilin gene is created that encodes a new protein version of itself, which helps M. bovis avoid recognition by the immune system. Pilin gene inversions have been thought to be a relatively rare process. However, we saw evidence that multiple M. bovis strains were undergoing the inversions during our study. This makes the pilin gene a challenge to use as a target and emphasizes why the outer membrane proteins identified in this study are an important discovery.”
The team sequenced M. bovis strains isolated from cattle from seventeen U.S. states and one Canadian province that were assembled by Dustin Loy, UNL professor and veterinary diagnostic microbiologist.
“The first finished genome of M. bovis was produced by this collaboration on an experimental strain in 2018,” said Loy. “Since then, we haven’t seen much progress in comprehensive sequencing of this bacterium until this study between ARS and UNL.”
“This disease is often overlooked. Still, it is the most frequently reported disease in beef breeding cows and second in calves. Our work recognizes the economic impact this causes to beef producers,” added Loy.
Article: Wynn, E. L., Hille, M. M., Loy, J. D., Schuller, G., Kuhn, K. L., Dickey, A. M., Bono, J. L., Clawson, M. L., 2022. Whole genome sequencing of Moraxella bovis strains from North America reveals two genotypes with different genetic determinants. BMC Microbiology, 22(1), 258, doi: 10.1186/s12866-022-02670-3