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Abstract The numerous ephemeral glacial meltwater streams that flow during the summer in the McMurdo Dry Valleys of South Victoria Land, Antarctica, provide habitats for microbial mats. One of the common mat types is composed of Chlorophyta (colloquially known as a ‘green mat’ due to its colour). While the presence of these mats is regularly monitored, their taxonomic makeup is still under investigation. Using 18S rRNA gene sequencing, the composition of the chlorophyte-dense mats from between rocks and in the main channel from several streams across two valleys was examined. Samples were maintained in native stream water, and select samples from representative locations were transferred to Bristol Medium. The appearance of other eukaryotic species - diatoms and tardigrades - in these green mats completed this integrated study. The results show that the relative abundance of Chlorophyta was significantly increased with the introduction of inorganic nitrogen from Bristol Medium. Chlorophyte taxa in theHazeniaandPleurastrumgenera dominated the samples across both sample types (rock or exposed) and treatments (Antarctic water or Bristol Medium). Furthermore, a reduction in overall sample diversity was observed in samples in Bristol Medium, suggesting preferential nitrogen utilization by these chlorophytes.
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Variation in pH gradients and FLO11 expression in mat biofilms from environmental isolates of the yeast Saccharomyces cerevisiae
Abstract Saccharomyces cerevisiaeproduces 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. This process creates a characteristic floral pattern and generates pH and glucose gradients outward from the center of the mat. Mats are encapsulated in a liquid which may aid in surface spreading and diffusion. Here, we examine thirteen environmental isolates that vary visually in the phenotype. We predicted that mat properties were universal and increased morphological complexity would be associated with more extreme trait values. Our results showed that pH varied significantly among strains, but was not correlated to mat complexity. Only two isolates generated significant liquid boundaries and neither produced visually complex mats. In five isolates, we tracked the initiation ofFLO11using green fluorescent protein (GFP) under the control of the endogenous promoter. Strains varied in when and how much GFP was detected, with increased signal associated with increased morphological complexity. Generally, the signal was strongest in the center of the mat and absent at the expanding edge. Our results show that traits discovered in one background vary and exist independently of mat complexity in natural isolates. The environment may favor different sets of traits, which could have implications for how this yeast adapts to its many ecological niches.
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- Award ID(s):
- 1839555
- PAR ID:
- 10379323
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- MicrobiologyOpen
- Volume:
- 11
- Issue:
- 2
- ISSN:
- 2045-8827
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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