Myxococcus xanthus - The Swarming Bacteria

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By [Patrick Nally]

Introduction

Myxococcus xanthus is a specific species of myxobacteria that are single celled but exist in “swarms” or “packs”. Myxococcus xanthus are rod-shaped and are gram-negative. M. xanthus was discovered in 1892 by Roland Thaxter. [1] M. xanthus are found in soil or any place plentiful with organic matter. They live best when the ph of the soil is around 7-8 and the temperature is around 30C. [2] M. xanthus is also a chemoorganotroph, which means they are organisms that oxidize the chemical bonds in organic compounds that they then use for energy. Myxococcus xanthus live together by living in a small biofilm or slime sheet. [3] They move as one in search of nutrients, but when nutrients are not immediately available the cells are able to transform and come together as one large mass in order to survive.

Classification


Kingdom: Bacteria

Phylum: Proteobacteria

Class: Delta Proteobacteria

Order: Myxococcales

Family: Myxococcaceae

Genus: Myxococcus

Species: M. xanthus

Ecology & Genome


Myxococcus xanthus is found in the Myxococcales order. Myxococcales can be characterized by the following: have specific ways of communicating with each other and are very social, they are morphogenetic, and they are able to move around via gliding. Many of these requirements for being in this order can be due to the habitat and nutrient availability. The gliding helps locate and attack other organisms within their general area. Myxococcus xanthus is also considered a predator since they eat other microbes in their environment. Myxococcus xanthus has been described as a social bacteria as well. [4] This means that each cell relies on each other in order to survive.

All myxobacteria, with one exception, have the largest genomes in comparison to other prokaryotes. Since myxobacteria are so complex and organized the large genome could be due to how they survive and live in harsh environments. [5] Since they are able to live together in tough conditions the genomes have high plasticity which results in changes in the genome such as the formation of the fruiting body. Four different myxobacteria species genomes were compared and it was found that 452 genes were found in all of them. [6] This means that these genes could be responsible for the formation of the fruiting body.

Myxococcus xanthus had its genome sequenced IN 2001 and it was found to be 9.14 Mb. This is much larger than other deltaproteobacteria. It was found that specific genes were selected for rather than random gene duplication. These genes included sensing for small molecules, transcription control, and cell to cell signaling. [7] The entire genome consists of 7,500 genes in total. Myxococcus xanthus also contains genes that aid in synthesizing amino acids as well as secreting growth inhibitors. There is also recent evidence that Myxococcus xanthus has a mechanism for breaking down protein. [8] It has also been found that fluids located within Myxococcus xanthus are able to lyse cell wall by hydrolyzing the peptidoglycan. [8] Each cell is only able to secrete so much, hence the reason they travel together in groups.


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