The Microbiology Department is pleased to announce that Ronnie Fulton of the Downs Lab is the recipient of a 2021-2022 NIH T32 Genetics Training Grant! For more information please click here.

The Microbiology Department is excited to announce that Andrew Wiggins, Summers Lab, is a recipient of the 2020-2021 ETA Award! The Center for Teaching and Learning administers the Excellence in Teaching Award (ETA), sponsored by the Graduate School. This highly competitive award recognizes teaching assistants who contribute to teaching at UGA beyond their own assigned classroom responsibilities. The ETA is the top teaching award for graduate students at UGA. Congratulations Andrew!

Abstract:

CRISPR loci are composed of short DNA repeats separated by sequences that match the genomes of phages and plasmids, known as spacers. Spacers are transcribed and processed to generate RNA guides used by CRISPR-associated nucleases to recognize and destroy the complementary nucleic acids of invaders. My postdoctoral work focused on 2 elements of this immune response: (1) Although, CRISPR-cas loci are widely distributed throughout microbial genomes and often display hallmarks of horizontal gene transfer, the drivers of CRISPR dissemination remain unclear. I show that spacers can recombine with phage target sequences to mediate a form of specialized transduction of CRISPR elements. (2) To counteract CRISPR defense, phages can produce small proteins that inhibit these nucleases. I demonstrate that the ΦAP1.1 temperate phage first expresses a canonical anti-CRISPR, to prevent Cas9 function, and then integrates into the direct repeats of the CRISPR locus to neutralize immunity during lysogeny. Building on these findings, I plan to characterize the interaction between CRISPR immunity and horizontal gene transfer, while also expanding this dynamic to determine wide-ranging mechanisms and barriers to horizontal gene transfer and how this impacts the pathogenicity of Staphylococcus and Streptococcus organisms.

Abstract:

Since the inception of life on Earth ~3.8 billion years ago, microorganisms have shaped and defined Earth’s biosphere and have created conditions that allowed the existence of all higher trophic life forms, including human societies. The microbial ‘unseen majority’ drives nearly all biogeochemical cycles. However, given their immense diversity, complex interactions and varied responses to environmental changes, we still have a limited understanding on how microorganisms affect climate change (including the production and consumption of climate-active molecules) and how they in turn will be affected. In this talk, I will focus on two research topics in the context of global carbon and sulfur cycles. The first study elucidates the molecular mechanisms of how methanogenic Archaea metabolize methylated sulfur compounds. The second study concentrates on marine bacterial communities that associate with marine phytoplankton cells. These projects demonstrate the power of integrating physiological and ecological approaches to understand microorganism–climate connections, which are essential for achieving an environmentally sustainable future.

The Microbiology Department is happy to announce that we have THREE Summer Research Grant recipients! Congratulations to Alyssa Baugh, Michael Mills, and Amy Siceloff!

We would like to congratulate Michael Mills and Tao Wang on receiving the Outstanding Teaching Assistant Award for 2020-2021! The Center for Teaching and Learning administers the Outstanding Teaching Assistant (OTA) award, sponsored by the Office of the Vice President for Instruction. This award recognizes teaching assistants who demonstrate superior teaching skills while serving in the classroom or laboratory. Way to go Michael and Tao!!

Abstract:

Single-stranded DNA phages of the family Microviridae have fundamentally different evolutionary origins and dynamics than their more frequently studied double-stranded DNA counterparts. Despite their small size (generally <5kb), which imposes extreme constraints on genomic innovation, microviruses have adapted to become prominent components of viromes in numerous ecosystems and hold a dominant position among viruses in the human gut. Yet until recently, they were known almost exclusively from metagenomic sequence data. By in-vitro synthesizing and transforming their miniature genomes into an E. coli host, I develop an experimentally tractable host-virus system that allows their study in the laboratory. Through building microviruses with combinations of genomic segments from different phages (mimicking diversity observed in natural populations), their interactions with each other and with their hosts can be recreated. Using this approach, I discover the role of a hypervariable genomic region in prophages that defends their hosts against infection by other members of the microvirus population. By detecting microviruses in metagenomic and genomic datasets, I show that this hypervariable region has evolved multiple times independently in response to the preceding evolution of lysogenic ability. These results provide a rare insight into the biology of these elusive phages and emphasize the importance of virus-virus interactions in viral evolution in general. The establishment of a microviral model system also paves the way for gaining a more thorough understanding of the roles of microviruses in the larger ecosystem of the human gut and elsewhere.

Abstract:

The paradigm has been that reactive oxygen species are toxic to bacteria. Indeed, an important strategy by which immune cells like neutrophils control and eliminate invading microbes is through synthesizing bleach (HOCl), the same chemical used as a household disinfectant. However, bacteria that colonize animals are not passive players and have evolved their own counter strategies to manipulate and repurpose reactive oxygen species in surprising ways. My research focuses on pro-inflammatory bacteria that have acquired robust antioxidant defenses sufficient to colonize inflamed tissue and tolerate millimolar concentrations of bleach. I will discuss my discovery that some pathogenic bacteria are attracted to bleach, which is potentially a mechanism by which they seek and acquire nutrients from damaged host tissue.