A lot can happen after a few drinks: Saccharomyces hybridization


We may have to reevaluate whether Saccharomyces cerevisiae alone is the species used to brew beer.  A paper from Gonzalez et al describes results from PCRRFLP comparison of 24 brewing strains identifies evidence for S. cerevisiae x S. kudriavzevii hybrids.  Although this hybridization is not unprecedented, most seem to be related to cultivated brewing or fermentation strains.  It seems that the hybrids are better able to cope with the stress associated with fermentation process.

Sacch tree

It seems these would also be a great test system for more whole genome sequencing or at least more polymorphism comparisons to try and determine the proportion of the genome that comes from different parents and estimate timing and frequency of hybridization.  It seems possible that the hybridizations are occurring multiple times in nature so are the same regions from each parental genome kept in the hybrid offspring that are selected for fitness under fermentation stress?

Gonzalez, S.S., Barrio, E., Querol, A. (2008). Molecular Characterization of New Natural Hybrids of Saccharomyces cerevisiae and S. kudriavzevii in Brewing . Applied and Environmental Microbiology, 74(8), 2314-2320. DOI: 10.1128/AEM.01867-07

Schizosaccharomyces genomes

S.octosporusThe Broad Institute has made available the Schizosaccharomyces octosporus genome sequence producing another model system (S.pombe) with several related species for comparative genomics.  I believe S. octosporus genome was entirely sequenced with 454 technology.   The other genome sequences in the Taphrina clade include the S. japonicus genome. S. octosporus is pretty interesting as it grows filamentously and is 8-spored unlike S. pombe. The origin of this filamentous growth would be quite important to understand how reversions to simpler fission yeast forms form and whether this is loss of whole gene families or remodeling of gene networks.

There is also some preliminary (old) sequence from Pneumocystis (although it is hard to track down that sequence, a paper from 2006 says there is draft sequence but none shows up in GenBank).  

See also:


More RIP without sex?

In followup to the Aspergillus RIP paper discussion, Jo Anne posted in the comments that her paper published in FGB about RIP in another asexual species of fungi also found that evidence for the meiosis-specific process of Repeat Induced Point-mutations (RIP).

Continue reading More RIP without sex?