Publications by authors named "Todd J Widhelm"
Mol Phylogenet Evol
September 2023
Article Synopsis
- Phylogenetic methods reveal evolutionary links and diversification trends among various taxa, particularly regarding the lichenized fungus genus Sticta in the Caribbean, where this study focuses on identifying ancestral ranges and species relationships.
- The research, encompassing data from the Greater and Lesser Antilles, shows a significant level of island endemism (around 59%) and suggests that the Caribbean was colonized approximately 19 million years ago from a South American ancestor, with some reverse migrations noted.
- Findings highlight that environmental factors have a stronger influence on taxonomic and phylogenetic diversity between island communities than geographic distance, emphasizing the critical role of islands in supporting global lichen biodiversity.
Article Synopsis
- The study focuses on Parmeliaceae, the largest family of lichen-forming fungi, analyzing 250 out of 350 genes to understand its phylogeny across various clades.
- By employing various analytical methods, the researchers found strong support for the monophyly of two subfamilies and seven major clades within Parmelioideae, as well as notable backbone relationships.
- The genus Parmotrema was identified as polyphyletic, leading to the proposal of reclassifying some species into a new genus called Crespoa, highlighting the effectiveness of reduced genome-scale data in phylogenetic research.
Mol Phylogenet Evol
September 2020
Article Synopsis
- Sticta, a fungal genus, forms symbiotic relationships primarily with green algae or cyanobacteria, with some species having associations with both types simultaneously.
- The study explored the diversity of green algal partners in Sticta across various global locations, revealing multiple genera of algae, with Heveochlorella being the most prevalent.
- Geographic factors significantly influence fungal-algal partnerships in Sticta, and while fungal and algal phylogenies showed some alignment, the study found no evidence for cospeciation, indicating that other evolutionary events such as host-switching played a role in these associations.
J Bacteriol
December 2019
Article Synopsis
- The death and lysis of specific bacterial cells during biofilm development release extracellular DNA, benefiting the entire bacterial community, and this process is influenced by the CidR transcriptional regulator.
- This study identifies crucial elements for the induction of a specific operon, highlighting the roles of CidR and the catabolite control protein A (CcpA) in regulating gene expression linked to carbon metabolism.
- Experimental results show that both CidR and CcpA are necessary for the operon's full expression, emphasizing a complex interaction of these regulators based on the bacteria's metabolic state.
Article Synopsis
- Advances in next-generation sequencing have greatly increased the number of loci for phylogenetic analysis, yet many studies still show significant gene-tree discordance due to historical factors like rapid diversification and gene duplication.
- Our study focused on 13 genera in the Lobariaceae family, analyzing 400 single-copy nuclear genes to assess the effects of data types (nucleotide vs. amino acid) and phylogenetic methods (species tree vs. concatenation) on evolutionary relationships.
- We found that incongruences in phylogenetic trees were linked to the type of sequence data and reconstruction method, with evidence of rapid diversification occurring around the Cretaceous-Paleogene boundary, which complicates the understanding of evolutionary relationships within the Lobariaceae
Mol Phylogenet Evol
September 2018
Article Synopsis
- Evolutionary biologists face challenges in understanding biodiversity, as the factors influencing organism diversification vary across time and space, and it's unclear which have the most significant effects.
- The study focused on the lichen genus Sticta, revealing its origin around 30 million years ago, but geographic origin estimates were inconclusive; high dispersal rates were noted, particularly in Hawaii where multiple colonization events occurred.
- Investigations into symbiont interactions showed that previous positive findings were largely due to statistical errors, while an analysis indicated that tectonic activity in the Andes could actually enhance the speciation rates of Sticta species.
Article Synopsis
- * PHB deficiency was found to lower the energy levels in cells and disrupt the flow of carbon into critical metabolic processes, negatively affecting the formation of essential spore components.
- * Supplementing PHB-deficient cells with fatty acids improves sporulation, demonstrating the interconnectedness of the TCA cycle and lipid biosynthesis in the sporulation process for Bacillus species.
Methods Mol Biol
August 2016
Article Synopsis
- * By sequencing the insertion sites, scientists can identify which genes are affected and create mutant libraries to study the roles of nonessential genes in biological processes.
- * This text outlines methods for creating a specific type of transposon mutant library using the mariner-based transposon bursa aurealis in the bacteria Staphylococcus aureus and S. epidermidis.
Article Synopsis
- Bacterial biofilm development benefits from the programmed death of certain cells, but the mechanisms behind this process are not well understood on a larger scale.
- The study identifies how two metabolic pathways, CidC and AlsSD, regulate cell death during the formation of staphylococcal biofilms, with CidC inducing cell death and AlsSD counteracting this effect.
- The findings suggest that the process of cell death in bacteria shares similarities with programmed cell death in eukaryotes and influences both biofilm growth and related disease outcomes, indicating a fundamental role for metabolic control in bacterial development.
Methods Mol Biol
June 2014
Article Synopsis
- Transposon mutant libraries are essential tools for studying hard-to-manipulate bacteria like Staphylococcus epidermidis, which currently lacks a sequence-defined mutant library.
- Previous research on S. aureus has laid the groundwork, but S. epidermidis has unique traits, particularly in how it adheres and forms biofilms.
- The study discusses modifications to existing methods for creating mutants in S. epidermidis using a specific transposon called bursa aurealis.
Article Synopsis
- * Mutations in the ackA and pta genes severely inhibit bacterial growth and increase cell death, yet the mutants maintain higher levels of ATP and NADH, suggesting a complex relationship between energy status and metabolic pathways.
- * Disruption of the Pta-AckA pathway elevates glucose consumption and activates the CidR regulon, indicating alternative metabolic pathways might help mutants survive despite impaired regulation of pyruvate metabolism.
Article Synopsis
- The Nebraska Center for Staphylococcal Research has created a library of 1,952 transposon mutants of the CA-MRSA strain USA300, each with a unique mutation in a nonessential gene, enhancing research capabilities for studying Staphylococcus aureus.
- The library was tested for various phenotypic traits like hemolytic potential and protease production, revealing known and novel genes linked to these processes.
- This resource highlights the discovery of previously unrecognized gene functions and provides a basis for future antibacterial research against Staphylococcus aureus, a significant human pathogen.
