nikita_gerasin's Favorites

Mag. 100x

• A pond-side water sample was taken on 07/31/2023 using a 10µ dip net to enrich for microbes. Air temp. 75°F.

Flatworm? Insect larva? Looks like it has retractable landing gear! :o) (i.e., the 4 objects surrounding the central, vesiculate oval object).

More phages from the deep water of this tea-stained lake. The first shot is of a bacterium captured at the moment of rupture by tailed phages. It looks like they made a pretty efficient transfer of bacterium to phage biomass. The burst size of 10 (if none were lost) is in line with other observations from nutrient-poor lakes. Next is a close-up of a tailless phage. The capsomeres are clearly evident, suggesting that this one is a single-stranded DNA virus of the Microviridae (I'm just guessing here). Number three has a long, non-contractile tail. That makes it a siphovirus. Four appears to have a contractile tail that will allow it to inject its DNA hypodermic-style. Nice head. Then two attached phages. Many bacterial cells seemed to have attached phages - hard to explain. Finally, an interesting community of viruses, tailed and tailless, on what might be a conjugation tube that is used to transfer DNA between bacterial cells. Conjugation is a handy way to pass on genes to confer immunity to phages. But it comes with a tradeoff - phages attach to the tube to inject their own nucleic acids. I like the curious structure of the lengthened icosahedra (?) of some of the phages.

I thought it would be fun to start putting some unusual records of free-living microbial interactions, made using different sorts of microscopy. This one is from the hypolimnion of a dystrophic lake, Lac Croche, at the UdeM field station. What is going in this photo captured by electron microscope? I think the large cell is a photosynthetic bacterium, I don't remember which sort. I suspect that it is not happy. Its coat is covered with bacteriophage particles. Look at the blow-up and you will see their icosahedral head shape (which looks hexagonal in profile). They're tiny, and tailless, so I'm thinking RNA viruses (Orthornavirae). We don't know if the viruses are coming or leaving - probably the latter. Some other kind of bacteria have docked on the photosynthetic bacterium's side. They might be friends or they might be foes, we shouldn't jump to conclusions. But it sure looks like some kind of savanna-level takedown.

I have my Bio 302L students at Northern Kentucky University to thank for this fun find. This amazing bacteria colony grew out of a water sample taken from the Lakeside Commons pond, directly behind the Campbell County Cooperative Extension offices. On 1/17, water and a little sediment was collected from the edge of the pond. On 1/19/2023 my microbiology students diluted a sample and spread plated it onto glycerol yeast-extract media, which is selective for gram-positives such as actinomycetes. This colony grew quietly on a 0.01 mL plate that had been forgotten in the fridge. Actinomycetes often have strange colony morphologies, so that's my guess on an ID for this. Neither I nor my colleagues have seen a colony like this before.

We found Trichoplax at Portobello Marine Lab (University of Otago) in November 2019, using microscope slides suspended in a display tank. We tried to cultivate them but lost them during Covid-19 lockdown. Found another one today. In total we have found 4, all of them are about 100um in diameter. We have video which makes us confident that this is Trichoplax (not a giant marine amoeba). If we can trap more and/or breed this one we will do DNA analysis to confirm that it is Trichoplax and whether it is a known (e.g. adherens) or new species.