Hannah writes:

Dear TWiM hosts,

My lab’s journal club is doing this paper today, and I thought it’d be a good fit for TWiM (or maybe even TWiEVO). It’s about insect endosymbionts that regulate their own virulence through quorum sensing. Basically, at the beginning of the infection, the bacteria produce a lot of toxins, but when they sense that they’ve colonised (thanks to quorum sensing molecules), they suppress all those virulence factors. This allows them to establish a persistent infection without further injuring the host. All of this has implications for how mutualistic relationships with microbes can arise, which I think is pretty cool!




Josh writes:

Hello Vincent!

I have been enjoying your show for several years now. I think your show’s conversational style and exploration of topics allows for people of all backgrounds to enjoy complex topics related to biology. Every one of your hosts in the TWIM/V/P has a knack for presenting material very clearly and your passion and excitement for the field is infectious.

Your discussion in TWIM 166 about the PNAS paper “Contemporary H3N2 influenza viruses have a glycosylation site that alters binding of antibodies elicited by egg-adapted vaccine strains” was fascinating. I wanted to see if you had any speculations about why the egg environment might select for this glycosylation site mutation in HA.   

Thanks again for for the podcasts.

I wanted to suggest a pick of the week:

This is quite the hobby for anyone interested in microbiology or likes pretty things.


Thank you,


Joshua Travis Renfroe, MS, MPH

Ph.D. Candidate

Georgia State University

Applied and Environmental Microbiology

Anthony writes:

Raw pet food as a risk factor for shedding of extended-spectrum beta-lactamase-producing Enterobacteriaceae in household cats.


I was surprised to learn that quite a few people feed their cat raw food exclusively.  In addition to the bacteria, there’s the public health hazard of toxoplasma.  Yes, freezing does kill a high proportion of the bradyzoites.  In Russian roulette, a high proportion of the chambers in the gun’s cylinder are empty.  That doesn’t make it a good idea.

Richard writes:

Hi esteemed professors,

I haven’t written in for a time, having stopped listening for a few years. It wasn’t my choice, but due to a prolonged hospital stay.

First the weather here in Bristol uk, is 3 deg C, cloudy, with 5 km/h wind. There is a little snow on the ground that fell this morning.

Regarding cooling towers, a subject I know a little about from my water treatment background, I can fill in some of your questions from twim 165.

Wet cooling towers are indeed a risk for legionella, usually there is a dosing system, that constantly doses biocides into the cooling water. It’s often (in the uk at least) the failure to maintain this, that causes issues, plus as you say resistant bacteria still grow.

In the uk dry cooling towers are preferred, and yes, generally made from copper. These don’t use water, so are less problematic, but less efficient.

Vincent, as you say water towers are closed, and generally drinking water supplies are dosed with chlorine dioxide. The level of chlorine dioxide in the water should sterilise it and prevent any legionella.

Hope that proves informative.

Regards Richard


Thanks for all the work you do, particularly twiv and twim. Though I have a lot of catching up to do, I intend to listen to every episode. I’m slowly working through about 3 years worth while still in hospital.