The effect of cooperator recognition on competition among clones in spatially structured microbial communities.

In spatially structured microbial communities, clonal growth of stationary cells passively generates clusters of related individuals. This can lead to stable cooperation without the need for recognition mechanisms. However, recent research suggests that some biofilm-forming microbes may have mechanisms of kin recognition.

Selection on plastic adherence leads to hyper-multicellular strains and incidental virulence in the budding yeast.

Many disease-causing microbes are not obligate pathogens; rather, they are environmental microbes taking advantage of an ecological opportunity. The existence of microbes whose life cycle does not require a host and are not normally pathogenic, yet are well-suited to host exploitation, is an evolutionary puzzle. One hypothesis posits that selection in the environment may favor traits that incidentally lead to pathogenicity and virulence, or serve as pre-adaptations for survival in a host.

Variation in pH gradients and FLO11 expression in mat biofilms from environmental isolates of the yeast Saccharomyces cerevisiae.

Saccharomyces cerevisiae produces a multicellular phenotype, known as a mat, on a semi-solid medium. This biofilm phenotype was first described in the lab strain Σ1278b and has been analyzed mostly in this same background. Yeast cells form a mat by spreading across the medium and adhering to each other and the surface, in part through the variegated expression of the cell adhesion, FLO11.

Variation at an adhesin locus suggests sociality in natural populations of the yeast .

Microbes engage in numerous social behaviours that are critical for survival and reproduction, and that require individuals to act as a collective. Various mechanisms ensure that collectives are composed of related, cooperating cells, thus allowing for the evolution and stability of these traits, and for selection to favour traits beneficial to the collective. Since microbes are difficult to observe directly, sociality in natural populations can instead be investigated using evolutionary genetic signatures, as social loci can be evolutionary hotspots.

Variation in Filamentous Growth and Response to Quorum-Sensing Compounds in Environmental Isolates of .

In fungi, filamentous growth is a major developmental transition that occurs in response to environmental cues. In diploid , it is known as pseudohyphal growth and presumed to be a foraging mechanism. Rather than unicellular growth, multicellular filaments composed of elongated, attached cells spread over and into surfaces.

Biofilm formation and toxin production provide a fitness advantage in mixed colonies of environmental yeast isolates.

Microbes can engage in social interactions ranging from cooperation to warfare. Biofilms are structured, cooperative microbial communities. Like all cooperative communities, they are susceptible to invasion by selfish individuals who benefit without contributing.

Metaboloptics: Visualization of the tumor functional landscape via metabolic and vascular imaging.

Many cancers adeptly modulate metabolism to thrive in fluctuating oxygen conditions; however, current tools fail to image metabolic and vascular endpoints at spatial resolutions needed to visualize these adaptations in vivo. We demonstrate a high-resolution intravital microscopy technique to quantify glucose uptake, mitochondrial membrane potential (MMP), and SO to characterize the in vivo phentoypes of three distinct murine breast cancer lines. Tetramethyl rhodamine, ethyl ester (TMRE) was thoroughly validated to report on MMP in normal and tumor-bearing mice.

Harnessing the power of digital droplet PCR to conduct real-world microbial competitions.

The budding yeast, Saccharomyces cerevisiae, has a long and storied history as a model organism for genetic, cellular and molecular biological research. More recently, researchers have sought to understand the ecology and evolution of its sister species, Saccharomyces paradoxus, in part to put our vast knowledge of the model yeast into its natural context (Replansky et al. ).

Known mutator alleles do not markedly increase mutation rate in clinical strains.

Natural selection has the potential to act on all phenotypes, including genomic mutation rate. Classic evolutionary theory predicts that in asexual populations, mutator alleles, which cause high mutation rates, can fix due to linkage with beneficial mutations. This phenomenon has been demonstrated experimentally and may explain the frequency of mutators found in bacterial pathogens.

Dark field optical imaging reveals vascular changes in an inducible hamster cheek pouch model during carcinogenesis.

In this study, we propose a low-cost cross-polarized dark field microscopy system for vascular imaging to detect head and neck cancer. A simple-to-use Gabor-filter-based image processing technique was developed to objectively and automatically quantify several important vascular features, including tortuosity, length, diameter and area fraction, from vascular images. Simulations were performed to evaluate the accuracies of vessel segmentation and feature extraction for our algorithm.

A Potential Case of Reinforcement in a Facultatively Sexual Unicellular Eukaryote.

The origin of a new species requires a mechanism to prevent divergent populations from interbreeding. In the classic allopatric model, divided populations evolve independently and accumulate genetic differences. If contact is restored, hybrids suffer reduced fitness and selection may favor traits that prevent mistakes in mating, a process known as reinforcement.

Prezygotic isolation between Saccharomyces cerevisiae and Saccharomyces paradoxus through differences in mating speed and germination timing.

Although prezygotic isolation between sympatric populations of closely related animal and plant species is well documented, far less is known about such evolutionary phenomena in sexual microbial species, as most are difficult to culture and manipulate. Using the molecular and genetic tools available for the unicellular fungus Saccharomyces cerevisiae, and applying them to S. paradoxus, we tested the behavior of individual cells from sympatric woodland populations of both species for evidence of prezygotic isolation.

Yeast sex: surprisingly high rates of outcrossing between asci.

Background: Saccharomyces yeasts are an important model system in many areas of biological research. Very little is known about their ecology and evolution in the wild, but interest in this natural history is growing. Extensive work with lab strains in the last century uncovered the Saccharomyces life cycle.

Allopatric divergence, secondary contact, and genetic isolation in wild yeast populations.

In plants and animals, new biological species clearly have arisen as a byproduct of genetic divergence in allopatry. However, our understanding of the processes that generate new microbial species remains limited [1] despite the large contribution of microbes to the world's biodiversity. A recent hypothesis claims that microbes lack biogeographical divergence because their population sizes are large and their migration rates are presumably high [2, 3].

Mate choice assays and mating propensity differences in natural yeast populations.

In sexual microbes, mating occurs by fusion of individual cells. This complete fitness investment suggests that cell behaviour could potentially mediate prezygotic isolation between microbial species, a topic about which very little is known. To investigate this possibility, we conducted individual cell mate choice trials and mass-culture mating propensity assays with isolates from sympatric natural populations of the closely related yeasts Saccharomyces cerevisiae and Saccharomyces paradoxus.