Part V of the Aspergillus series! You made it! If this is your first visit to the blog, you’ve arrived at Part 5 of a weekly Aspergillus series. So far we’ve covered: Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, and Aspergillus versicolor. This week, I’m going to introduce you to Aspergillus glaucus. This one is interesting because it actually goes by two names. It is known as Aspergillus glaucus in it’s asexual state, but in it’s sexual state it’s known as Eurotium herbariorum. I’ve never said that word out load before…until just now. Kind of a mouthful, right? And I can’t believe my luck…I actually have photos of this fungus in both states.
Now, in general, Aspergillus species are pretty frequently encountered in the lab. Second only to Candida species. But Aspergillus glaucus? I hardly ever see it. I think I’ve seen it two….maybe three times. It is pretty widespread in the environment, found world wide but it prefers a dry environment. It rarely shows up in the lab, and causes infection even less frequently than that. It has been reported to occasionally cause infection of the nails and ears, and in cases where the patient is more severely immunocompromised it may cause infection in the brain , heart, or other internal organs.
Aspergillus glaucus is a slower grower than the other Aspergillus species that we’ve covered so far. This one takes as many as 7-21 days to reach maturity, and if you want to see ascospores those typically show up around 14 days. An interesting note, this species is an osmophilic fungus that loves sugars. The growth rate can be significantly expedited if it is placed on the appropriate growth media, such as one that contains 20% sucrose. Aspergillus glaucus loves sugars so much, it tends to cause bigger problems in food than it does in people. It is often found contaminating fruit, fruit juices, corn syrup, honey, and other sweet sticky liquids.
Macroscopically, this colony does not spread as much as other Aspergillus species. The surface is kind of feltlike in texture, and gets little nubbins (that’s a word, right?) with age. It’s described as “dull green” with yellow areas. The one I used for these photos I would specifically describe as grayish green with a yellow periphery. The reverse side of the agar can be white or yellow in color.
Microscopically, Aspergillus glaucus can have all kinds of stuff going on! We start with smooth conidiophores, medium in size compared to other Aspergillus. The vesicle bears uniseriate phialides which may be loosely radiate or loosely columnar. The conidia are a little larger and rougher than those of other Aspergillus species. And that’s just when it’s asexual. In the sexual state, Aspergillus glaucus becomes Eurotium herbariorum and exhibits large cleistothecia. The cleistothecia release ascopsores that have a little central groove that kind of make them resemble hamburgers.
Happy Valentine’s Day!
Instead of a sketch, I give you this Valentine. A beautiful experiment. I usually use Lactophenol Cotton Blue to stain my organisms, but on a whim I decided to try Eosin. I loved the result! It actually worked quite well…and it’s PINK!
Side note: I *would* have shown you Aspergillus nidulans this week, prior to showing you glaucus…but I don’t have any nidulans. I haven’t decided what to do about that yet…borrow photos or root around in the dirt. We’ll see.