Monday, April 15, 2019

BacterioFiles 382 - Small Scavengers Suck Sizeable Cells

Rhodotorula prey yeast
By A doubt, CC BY-SA 3.0
This episode: Fungus-hunting amoebas have different strategies for detecting and preying on single-celled and filamentous fungi!

Also, a personal note: I'm going to be taking a few weeks off the podcast to be able to take full advantage of spring, but I'll be back as soon as the weather gets too hot.

Download Episode (7.5 MB, 8.2 minutes)

Show notes:
Microbe of the episode: Chondromyces catenulatus

Takeaways
Amoebas in the microbial world are like powerful predators, going around gobbling up whatever they find that's small enough, by a process called phagocytosis, in which they surround their prey with their cell membrane and engulf it. It's similar to macrophages or white blood cells as part of our immune system in our bodies.

The prey of amoebas includes bacteria, large viruses, and single-celled fungi called yeasts. In this study, scientists showed that some yeasts make great food sources for a certain kind of amoeba called Protostelium aurantium, while others either lack nutritional value or hide from the predators by covering up certain recognition molecules on their cell wall.

They found that the amoebas could also consume the spores of filamentous fungi, and could even attack the filaments, or hyphae. In this latter case, instead of engulfing the large filaments, they pierced the cells and extracted their contents, an approach named ruphocytosis, from the Greek for suck or slurp.

Journal Paper:
Radosa S, Ferling I, Sprague JL, Westermann M, Hillmann F. The different morphologies of yeast and filamentous fungi trigger distinct killing and feeding mechanisms in a fungivorous amoeba. Environ Microbiol.

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Monday, April 8, 2019

BacterioFiles 381 - Chlorophyll Can Convey Cancer Characteristics

Tumor imaging by MSOT
By Peters et al. 2019,
Nat Commun 10:1191, CC BY 4.0
This episode: Pigmented bacteria can be used in a cancer imaging technique that combines light and sound!

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Show notes:
Microbe of the episode: Streptomyces bellus

Takeaways
Because "cancer" is a general term that describes many different forms of disease affecting different cells in different parts of the body, effective cancer treatment relies on understanding the location and physiology of the cancer in a given patient. New imaging technologies for diagnosis and analysis of cancer and for cancer research can be very valuable, especially if they don't require big investments of money and space.

One promising imaging technology is called multispectral optoacoustic imaging, or MSOT. This uses pulses of light to create vibrations as pigments in tissues absorb the light and undergo thermal expansion; these vibrations are then detected by ultrasound technology. This approach allows good resolution and depth of imaging without large equipment like MRI machines, but the best results require adding pigments into the body.

In this study, scientists showed that the photosynthetic pigments of purple non-sulfur bacteria can be useful in this optoacoustic imaging, providing a somewhat long-term, nontoxic approach. It proved especially interesting when they discovered that the wavelength spectrum changing over time was an indication of macrophage activity in the tumors.

Journal Paper:
Peters L, Weidenfeld I, Klemm U, Loeschcke A, Weihmann R, Jaeger K-E, Drepper T, Ntziachristos V, Stiel AC. 2019. Phototrophic purple bacteria as optoacoustic in vivo reporters of macrophage activity. Nat Commun 10:1191.

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Monday, April 1, 2019

BacterioFiles 380 - Plant Promoter Produces Polymer

Herbaspirillum-like bacteria
in banana plants
Scientific Figure on
ResearchGate. CC BY-NC 4.0
This episode: A microbe that boosts plant growth needs to make storage polymers for both itself and the plant's sake!

Download Episode (7.1 MB, 7.75 minutes)

Show notes:
Microbe of the episode: Suid gammaherpesvirus 3

Takeaways
Bacteria that promote plant growth are fascinating and not too hard to find. Plants and microbes make good partners by each contributing something the other needs. Plants make sugars via photosynthesis that microbes can use as food, and microbes can gather nutrients that plants can't make, can drive off pathogens, and can contribute to plant growth in other ways.

However, plants aren't making sugars all the time, because the sun goes down every day. So what do partner microbes do at these times? In this study, a beneficial microbe Herbaspirillum seropedicae was found to produce a storage compound called polyhydroxyalkanoate, or PHA, that it could use to store food for times of scarcity. Mutants of this microbe that could not make the storage compound weren't very beneficial for their plant partners.

Journal Paper:
Alves LPS, Amaral FP do, Kim D, Bom MT, Gavídia MP, Teixeira CS, Holthman F, Pedrosa F de O, Souza EM de, Chubatsu LS, Müller-Santos M, Stacey G. 2019. Importance of Poly-3-Hydroxybutyrate Metabolism to the Ability of Herbaspirillum seropedicae To Promote Plant Growth. Appl Environ Microbiol 85:e02586-18.

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Monday, March 25, 2019

BacterioFiles 379 - Photons Facilitate Faster Flourishing

This episode: Light increases the growth even of some bacteria that don't harvest its energy!

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Show notes:
Microbe of the episode: Methylococcus thermophilus

News item

Takeaways
Light from the sun is one of the fundamental sources of energy for life on this planet. Plants and other phototrophs—photosynthetic organisms that get their energy mainly from light—form the foundation of the food web, and organisms that feed on them or that feed on organisms that feed on them are all dependent on the ability to capture the sun's rays.

There are other ways to benefit directly from the sun's energy, besides photosynthesis—some microbes have enzymes that use light energy to repair damage to DNA (the same damage that is caused by ultraviolet light), and we use sunlight to synthesize vitamin D.

In this study, however, microbes are discovered to grow faster in the presence of light despite not being phototrophs or producing any light-harvesting proteins. The scientists discover some possible light-sensing proteins, though, that could regulate these microbes' behavior, allowing them to synchronize their growth cycles to phototroph partners in aquatic environments.

Journal Paper:
Maresca JA, Keffer JL, Hempel P, Polson SW, Shevchenko O, Bhavsar J, Powell D, Miller KJ, Singh A, Hahn MW. Light modulates the physiology of non-phototrophic Actinobacteria. J Bacteriol JB.00740-18.

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Monday, March 18, 2019

BacterioFiles 378 - Medusa Makes Marble Microbes

Medusavirus
Yoshikawa et al. 2019 J Virol.
This episode: Newly discovered giant virus from a hot spring turns its amoeba hosts to stone!

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Show notes:
Microbe of the episode: Listeria virus P70

News item

Takeaways
Viruses come in endless different shapes, sizes, and genetic configurations. Even within the group called giant viruses there is a large amount of variety. Many of their genes are unknown, without homology to any other sequences we have acquired in other areas of life. There is great potential to learn interesting things from these viruses.

In this study, a new giant virus is discovered. Like many others, this infects amoebas, and causes them to transform from dynamic, shape-shifting cells into hard little cyst-like circles. This ability gave it the name Medusavirus. It's the first giant virus found in a relatively hot environment (a hot spring), and among other interesting features, it shows signs of multiple instances of gene transfer to and from its amoeba host.

Journal Paper:
Yoshikawa G, Blanc-Mathieu R, Song C, Kayama Y, Mochizuki T, Murata K, Ogata H, Takemura M. 2019. Medusavirus, a novel large DNA virus discovered from hot spring water. J Virol JVI.02130-18.

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Monday, March 11, 2019

BacterioFiles 377 - Distributed Defense-Defeating Devices

This episode: Newly discovered CRISPR-inhibiting genes are found in many different bacterial groups!

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Show notes:
Microbe of the episode: Borrelia mazzottii

News item

Takeaways
The discovery of the microbial immune system, CRISPR-Cas, changed many things about the way we think of microbial ecology and interactions with microbe-infecting viruses. The CRISPR-Cas system can learn to detect new threats by capturing bits of their genetic sequences and using these to target the Cas proteins to chop up any such sequences that make it into the cytoplasm. This can greatly increase microbial survival in certain ecosystems in which viruses regularly kill a large percentage of the microbial population.

To overcome this defense, a virus has to adapt, either by acquiring mutations that change its sequence, thus escaping detection, or by acquiring anti-CRISPR proteins that shut down the microbial defense directly. These possibilities make the complex ecology even more interesting.

In this study, scientists develop a clever method for screening for new anti-CRISPR genes, and go searching for them in samples from various places (soil, animal guts, human gut). They find several new examples, which turn out to be found in many different kinds of species in many different environments.

Journal Paper:
Uribe RV, Helm E van der, Misiakou M-A, Lee S-W, Kol S, Sommer MOA. 2019. Discovery and Characterization of Cas9 Inhibitors Disseminated across Seven Bacterial Phyla. Cell Host & Microbe 25:233-241.e5.

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Monday, March 4, 2019

BacterioFiles 376 - Pressurized Pollutant Pulls Products

Bacillus megaterium
By Osmoregulator, CCBY-SA 3.0
This episode: Supercritical carbon dioxide and bacteria that can grow in it make a great combination for biofuel production!

Download Episode (9.4 MB, 10.2 minutes)

Show notes:
Microbe of the episode: Flexibacter aggregans

Takeaways
Biofuels are an important part of humanity's move away from non-renewable resources. They have a higher energy density than batteries are yet able to achieve, giving them significant advantages for transportation purposes in which tapping into an electric grid isn't possible. Depending on the biofuel, they also have the advantage of existing infrastructure: we don't need to build a whole new system of charging or refueling stations, but can use the systems already in place.

However, biofuels as a collection of technologies still need some refinements. Yields for the more potentially sustainable approaches are low, and the lower the concentration of a soluble fuel, the more difficult it is to separate it from the non-fuel components of a fermentation. Microbial products also face the risk of contamination of a fermentation by unwanted organisms that use up the substrate without producing desirable products.

In this study, supercritical carbon dioxide is considered as a fix for both of these problems. The gas is pressurized to a point at which it is indistinguishable from liquid. A strain of Bacillus megaterium is specially selected as capable of growing and fermenting in this environment, while contaminants are inhibited. The solvent potential of supercritical carbon dioxide also serves as a way to extract the biofuel product—in this case, isobutanol—from the aqueous part of the culture medium. While it needs some development, this approach yields promising results.

Journal Paper:
Boock JT, Freedman AJE, Tompsett GA, Muse SK, Allen AJ, Jackson LA, Castro-Dominguez B, Timko MT, Prather KLJ, Thompson JR. 2019. Engineered microbial biofuel production and recovery under supercritical carbon dioxide. Nat Commun 10:587.

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