Sean Callahan

University of Tennessee | UTK · Department of Microbiology

The discovery of neutrophil subtypes has expanded what is known about neutrophil functions, yet there is still much to learn about the role of these subtypes during bacterial infection. We investigated whether Campylobacter jejuni induced differentiation of human neutrophils into the hypersegmented, CD16hi/CD62Llo subtype. In addition, we investiga...

Histone modifications alter numerous cornerstone processes in eukaryotes, including metabolism, physiology, and immunity. Numerous bacterial pathogens can alter expression of host-derived sirtuins to deacetylate histones in order to promote infection, yet, a bacterial-derived sirtuin has yet to be investigated to deacetylate host histones. Using Ca...

The discovery of neutrophil subtypes has expanded what is known about neutrophil functions, yet there is still much to learn about the role of these subtypes during bacterial infection. We investigated whether Campylobacter jejuni induced differentiation of human neutrophils into the hypersegmented, CD16 hi /CD62L lo subtype. In addition, we invest...

Nucleases are ubiquitous in pathogens and allow bacteria to acquire nucleotide nutrients, take up foreign DNA, induce tissue damage, degrade neutrophil extracellular traps, and modulate the host inflammatory response. Furthermore, nucleases can modulate numerous bacterial virulence factors, promoting bacterial growth and disease. To understand how...

Campylobacter jejuni is the leading cause of bacterial‐derived gastroenteritis worldwide, infecting 96 million individuals annually. During infection, inflammation and tissue pathology occur in the lower gastrointestinal tract, including the recruitment of leukocytes. Neutrophils are the most abundant leukocyte in humans, and recruitment is associa...

Campylobacter spp. are the leading cause of bacterial-derived gastroenteritis worldwide, impacting ninety-six million individuals annually. Unlike other bacterial pathogens of the gastrointestinal tract, Campylobacter spp. lack many of the classical virulence factors that are often associated with the ability to induce disease in humans, including...

A previously identified transcriptional regulator in C. jejuni , termed HeuR, was found to positively regulate heme utilization. Additionally, transcriptomic work demonstrated the putative operons, CJJ81176_1390-1394 and CJJ81176_1214-1217, were upregulated in a HeuR mutant, suggesting HeuR negatively regulates expression of these genes. Because ge...

ANME-1 archaea subsist on the very low energy of anaerobic oxidation of methane (AOM). Most marine sediments shift from net AOM in the sulfate methane transition zone (SMTZ) to methanogenesis in the methane zone (MZ) below it. In White Oak River estuarine sediments, ANME-1 comprised 99.5% of 16S rRNA genes from amplicons and 100% of 16S rRNA genes...

Campylobacter jejuni is the leading cause of bacterial‐derived gastroenteritis worldwide and can lead to several post‐infectious inflammatory disorders. Despite the prevalence and health impacts of the bacterium, interactions between the host innate immune system and C. jejuni remain poorly understood. To expand on earlier work demonstrating that n...

Uncultured members of the Methanomicrobia called ANME-1 perform the anaerobic oxidation of methane (AOM) through a process that uses much of the methanogenic pathway. It is unknown whether ANME-1 obligately perform AOM, or whether some of them can perform methanogenesis when methanogenesis is exergonic. Most marine sediments lack advective transpor...