Eukaryotic Micro: Week 3 the last of the fungi

So this week (actually last week) we covered what is probably the last unit concerning fungi: Cryptococcus neoformans. The first two weeks covered two ascomycetes, Candida albicans and Fusaruim species, and now we move over to the basidiomycetes, otherwise known as 'if I asked you to draw a fungus this is what you would draw'.

The primary research papers were:

• Polyploid titan cells produce haploid and aneuploid progeny to promote stress adaptation. Gerstein AC, Fu MS, Mukaremera L, Li Z, Ormerod KL, Fraser JA, Berman J, NielsenK. MBio. 2015 Oct 13;6(5):e01340-15. doi: 10.1128/mBio.01340-15.
• Protein Composition of Infectious Spores Reveals Novel Sexual Development and Germination Factors in Cryptococcus. Huang M, Hebert AS, Coon JJ, Hull CM. PLoS Genet. 2015 Aug 27;11(8):e1005490. doi: 10.1371/journal.pgen.1005490. eCollection 2015 Aug.

This is an interesting point in the semester. Upon completion of this week, we are ~25% of the way through the semester and exactly 25% of the way through the 12 modules. This is the point where students have completed the short writing assignment four times now, so hopefully they are comfortable with what I am looking for. I lay out the guidelines on day 1, and then model what I expect. There are two difficulties. 1: Getting students to explain a dataset of their choosing such that someone would walk away knowing what was done, what it showed, and most importantly be able to ask informed questions about the data set. Students are reasonably good at explaining the data after a week or two, but struggle to give enough experimental information such that you would know how the data was obtained. 2: Identifying limitations with the data set. This is in fact difficult, but it is an important skill to foster if we really want people who are critical thinkers. I ask them that their limitation answers the question 'how does this affect the authors' conclusions or interpretations?' This latter issue usually takes a couple more weeks to get better at for most of the class.

Cryptococcus neoformans normal and titan cells

It's also interesting because Cryptococcus follows up the ascomycetes we already discussed extremely well. Like Candida albicans, C. neoformans is a budding yeast, which is distinct from Fusarium, which although more closely related to C. albicans, is a filamentous fungus. However, like Fusarium, C. neoformans forms dikaryotic filaments during sexual reproduction and grows in a filamentous form during asexual spore production. 

I like these two papers (this is the first year I've used the Gerstein paper) because they deal with different aspects of development/differentiation in different ways.  The Gerstein paper is focused on a role titan cells play using primarily genomic approaches; the Huang paper is focused on spore formation and development using classical genetic approaches.

Gerstein et al ties in conceptually with the Selmecki and Ma papers from the Candida and fusarium modules respectively. All are centered on the acquisition of additional genetic information and the outcomes of this. I'm certain creationists always talk about the inability for an organism to acquire new 'information'. Well here are three independent examples.

Huang et al ties in, slightly, with the Lui paper from the Fusarium module by dealing with cellular differentiation and development. This is something we will come back to in the future frequently and is a biological concept I think is often underappreciated in microbes.