Monday, October 26, 2020

436 - Copper Concentrates Culture Current

Geobacter sulferreducens
By Mantapia11147,
CC BY-SA 4.0
This episode: Copper electrodes, rather than killing bacteria in microbial fuel cells, allow them to generate higher densities of electric current!

Download Episode (5.0 MB, 7.2 minutes)

Show notes:
Microbe of the episode: Xipapillomavirus 2


Takeaways
Copper is widely used as a way to make surfaces and materials antimicrobial, to cut down on the spread of pathogens in hospitals and other environments. Among other mechanisms, it reacts with oxygen to form reactive oxygen species that are very harsh on microbial proteins. But copper is also a good electrical conductor, which would be useful to use in microbial fuel cells, which exploit bacterial metabolism to generate electricity. Microbes form biofilms on an electrode and transfer electrons to it as a way for them to generate energy. Most such fuel cells have used graphite electrodes to avoid toxicity.

In this study, fuel cell bacteria grew well on a copper electrode in an oxygen-free environment. The copper actually allowed them to increase the amount of current they produced per unit of area, as ionic copper diffused through the biofilm and allowed electrons to flow through the biofilm to the electrode from layers farther from the electrode that otherwise would not have access. Even graphite electrodes could be improved by adding these copper ions to the biofilm directly.

Journal Paper:
Beuth L, Pfeiffer CP, Schröder U. 2020. Copper-bottomed: electrochemically active bacteria exploit conductive sulphide networks for enhanced electrogeneity. Energy Environ Sci 13:3102–3109.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, October 19, 2020

435 - Invader Introducing Infrared Invokes Immunity

Mouse with darkened tumor
By Yi et al. 2020,
Sci Adv 6:eaba3546
CC BY-NC 4.0

This episode: Combining Salmonella with something called photoimmunotherapy to attack tumors in multiple ways!

Download Episode (8.2 MB, 11.9 minutes)

Show notes:
Microbe of the episode: Shimwellia blattae

Takeaways
Distinguishing healthy from unhealthy tissue is one of the big challenges when dealing with cancer. Since cancer is derived from healthy tissue, there are many similarities between them that make it hard to target it specifically. This is especially important when cancer is spread in multiple places throughout the body, as opposed to a single tumor that can be removed locally.

In this study, bacteria modified to make them safer were injected into mice with tumors. The bacteria alone were capable of doing some damage to the tumors, and this damage happened to make the tumors darker. Using this color change, the scientists targeted the tumors with lasers to heat them up and kill them in an isolated manner. This had the added benefit of inducing an immune response against the cancer that could target it throughout the body.

Journal Paper:
Yi X, Zhou H, Chao Y, Xiong S, Zhong J, Chai Z, Yang K, Liu Z. 2020. Bacteria-triggered tumor-specific thrombosis to enable potent photothermal immunotherapy of cancer. Science Advances 6:eaba3546.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, September 28, 2020

434 - Killer Carries Compact Cas

T4 bacteriophage
By Victoramuse
CC BY-SA 4.0
This episode: Large phage discovered that contains a compact version of the CRISPR/Cas defense/gene editing system!

Download Episode (5.9 MB, 8.6 minutes)

Show notes:
Microbe of the episode: Stenotrophomonas virus IME13

News item

Takeaways
CRISPR/Cas systems have made a lot of things in gene editing much easier in certain organisms. It's almost as easy as just getting the cells to produce the Cas protein and putting in an RNA sequence to tell it where to go! But in some cases, these requirements are too much to work well.

In this study, a more compact version of CRISPR/Cas was discovered in large bacteriophages. These systems help the viruses compete with other viruses and defend against host defenses sometimes. The Cas protein is half the size of the standard Cas most used in gene editing, and it has fewer other requirements to function in new cells, so it could be better in versatility and potential in applications with strict space constraints.

Journal Paper:
Pausch P, Al-Shayeb B, Bisom-Rapp E, Tsuchida CA, Li Z, Cress BF, Knott GJ, Jacobsen SE, Banfield JF, Doudna JA. 2020. CRISPR-CasΦ from huge phages is a hypercompact genome editor. Science 369:333–337.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, September 21, 2020

433 - Probiotic Promotes Pathogen Peacefulness

E. coli in lumen of organoid
From Pradhan and Weiss, 2020
mBio 11(4):e01470-20
CC BY 4.0

This episode: A probiotic can protect intestine-like cell growths from destruction by pathogens, but it can also be infected by a virus that makes it more harmful to intestinal cells!

Download Episode (6.9 MB, 10.1 minutes)

Show notes:
Microbe of the episode: Euphorbia yellow mosaic virus

News item

Takeaways
There are many strains of Escherichia coli. Some are pathogenic, in the gut or the urinary tract, and a subset of those are very dangerous, such as the enterohemorrhagic O157:H7 strain. Many others are commensals, living peacefully as part of our gut community. And some strains can be beneficial to the host, protecting from and reducing the severity of disease. One such strain is called E. coli Nissle.

This study used an advanced model of human intestines called organoids, where stem cells are induced to develop into hollow spheres of intestinal epithelium in which all cell types of a normal intestinal wall are represented. E. coli pathogens typically destroy these organoids and escape from inside, but Nissle was able to prevent this destruction and enable coexistence between the pathogen and the host cells. Nissle suffered for this protection though; O157:H7 carries a toxin-encoding phage that can infect and kill susceptible E. coli strains. Those Nissle cells that survived this infection could resist the phage, but were not as beneficial to the organoids due to the toxin they now produced.

Journal Paper:
Pradhan S, Weiss AA. 2020. Probiotic Properties of Escherichia coli Nissle in Human Intestinal Organoids. mBio 11(4):e01470-20.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, September 7, 2020

432 - Moses Microbes Maintain Moisture

Gypsum
This episode: Bacteria living in the driest place on earth have ways to extract water from the mineral structures of rocks!

Download Episode (3.7 MB, 5.4 minutes)

Show notes:
Microbe of the episode: Irkut lyssavirus

News item

Takeaways
Microbes living in extremely dry conditions have it tough. Water is important both for the chemistry and structure of all cells. Desert microbes are very good at acquiring and holding on to the water they can find, but in places such as the Atacama Desert in Chile, there's almost none available.

However, microbes can be very resourceful. In this study, phototrophs were discovered that can actually extract water molecules bound up in the crystalline structure of the mineral gypsum, and this allows them to survive in hyperarid regions. They do this by secreting organic acid molecules to etch the rock and release the water, converting gypsum to anhydrite, which is a mineral with the same chemical structure except without the water.

Journal Paper:
Huang W, Ertekin E, Wang T, Cruz L, Dailey M, DiRuggiero J, Kisailus D. 2020. Mechanism of water extraction from gypsum rock by desert colonizing microorganisms. Proc Natl Acad Sci 117:10681–10687.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, August 31, 2020

431 - Conductive Cables Control Carbon

Cable bacteria around
plant roots
From Scholz et al. 2020
Nat Commun 11:1878

This episode: Cable bacteria around rice roots transport electrons and help prevent formation of methane!

Thanks to Vincent Scholz for his contribution!  
Download Episode (5.7 MB, 8.3 minutes)

Show notes:
Microbe of the episode: Vibrio alginolyticus

News item

Takeaways
Transforming other things into methane is a great way to make a living for some kinds of microbes. These tend to live under still water, like in rice fields or wetlands, or in the guts of cattle. And while this methane could be useful as natural gas if collected, it's a much more potent greenhouse gas than carbon dioxide when released into the atmosphere.

In this study, cable bacteria were inoculated into rice pots in the lab. Cable bacteria transfer electrons from deeper down in the ground up to the surface to generate energy, and in the process generate sulfate. This sulfate allows other microbes to outcompete the methane producers, reducing the amount of methane produced from rice cultivation in the lab. This may be helpful to reduce greenhouse gas emissions from rice agriculture.

Journal Paper:
Scholz VV, Meckenstock RU, Nielsen LP, Risgaard-Petersen N. 2020. Cable bacteria reduce methane emissions from rice-vegetated soils. 1. Nat Commun 11:1878.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.

Monday, August 24, 2020

430 - Dextrose Deposits Delay Dormancy

E. coli
This episode: Bacteria that can store sugar as glycogen have multiple advantages when food is only available sporadically!
Download Episode (7.2 MB, 10.4 minutes)

Show notes:
Microbe of the episode: Carnivore bocaparvovirus 3

Takeaways
Almost all habitats experience some sort of change and fluctuation; very few are totally stable, depending on the timeframe. So strategies to change and adapt with changing conditions can greatly help an organism thrive. For example, methods of storing energy are helpful when food is only available sporadically.

Some bacteria, like humans, can store sugar in a polymer called glycogen, which can be quickly produced when food is abundant and quickly broken down to ease a transition to fasting. In this study, bacteria that could produce and use glycogen were able to stay active longer and grow better in the face of intermittent starvation. They were even better able to acquire new food when more became available.

Journal Paper:
Sekar K, Linker SM, Nguyen J, Grünhagen A, Stocker R, Sauer U. 2020. Bacterial Glycogen Provides Short-Term Benefits in Changing Environments. Appl Environ Microbiol 86.

Other interesting stories:

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.