Natures wonders: predators among bacteria (Introduction)

by David Turell , Friday, October 18, 2024, 17:13 (34 days ago) @ David Turell

War at a microscopic level:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/18_october_2024/422...

"Where a resource (food) exists, nature will find a way to exploit it. This is no different at the microscopic level, and although study of microbial predation is much less common, there are several model predatory bacteria. These include Bdellovibrio bacteriovorus, a bacterium that invades the periplasm of Gram-negative bacteria, and Myxococcus xanthus, a predator capable of both single-cell, contact-dependent killing and multicellular “wolf pack” behavior involving coordinated movement of a group of predator cells.

***

"The term ixotrophy was coined by microbiologist Ralph Lewin (2) to describe how marine filamentous Saprospira bacteria catch their prey using a sticky surface (the Greek root ixo means sticky). The microscopy of Lewin detailed several prey cells distributed along the length of one predator, a ratio distinct from Bdellovibrio predation, where a small predator consumes a large prey. Using a combination of techniques, Lien et al. characterized the spectrum of ixotrophic behavior in the related Aureispira sp. CCB-QB1 (hereafter referred to as Aureispira), which preys on bacteria such as Vibrio sp. in seawater. The authors specifically sought to understand how prey is caught and killed, how this mechanism is regulated, and why cells use ixotrophy.

***

"...ixotrophy-mediated killing requires direct cell-cell contact, either by gliding motility on solid surfaces or by immobilization of prey on the Aureispira cell surface in liquid media.

"In both environments, prey cells quickly die by lysis after contact. The authors used cryo–electron tomography to identify the structures involved in prey catching and killing. They found that Aureispira have large molecular machines associated with their cell envelopes, including numerous rigid rods with terminal grappling hook structures that appear to facilitate cell-cell contact between Aureispira and V. campbellii in liquid culture.

***

"Electron microscopy of Aureispira also revealed multiple type VI secretion systems (T6SSs)—contractile, needlelike structures used by many Gram-negative bacteria to inject harmful proteins into other cells. Lien et al. observed that contracted T6SSs expelled their inner tube and punctured the prey cell, which became rounded in shape, consistent with breakdown of their cell walls. Single-cell analyses with stable isotope–labeled prey showed that prey components were taken up by the predator after puncture.

***

"A glance at bacteriophage may also explain why Aureispira target the flagellum. Flagellotropic bacteriophage (11) are thought to do so because the presence of flagella correlates with fitness of the cell, hence signaling a “worthwhile” prey. The size of the flagellum renders it a more effective target than the cell body, particularly in an aquatic medium. Together, the broad and insightful characterization of ixotrophy by Lien et al. has the potential to stimulate many more molecular insights into the underappreciated predation events that shape bacterial populations in the environment."

Comment: it is dog-eat-dog all the way down to microscopic predators who surprisingly have a Amory of different physical and chemical weapons. Download the article to see the physical weapons illustrated.