Scientists have discovered a gene necessary for the unusual lifestyle of tiny bacteria that live on the surface of larger bacteria. Companion bacteria are a mysterious group of tiny microorganisms whose ways of life are elusive. Although scientists can only cultivate a few of these species, they are part of a diverse family found in many environments.
Scanning electron micrograph shows small purple Corynebacterium cells growing on the surface of a much larger cell. New research led by the laboratory of Joseph Mougous at UW Medical Center in Seattle reveals their life cycle, genes, and some of the molecular mechanisms behind their unusual lifestyle. These epiphytic bacteria are Southlakia epibionticum. Image credit: Yaxi Wang, WaiPang Chan, and Scott Braswell/University of Washington
The few species of Corynebacterium that researchers were able to grow in the lab live on the cell surface of another, larger host microbe. Corynebacteria generally lack the genes needed to make many of the molecules necessary for life, such as the amino acids that make up proteins, the fatty acids that form membranes, and the nucleotides in DNA. The researchers speculated that many invertebrates rely on other bacteria to grow.
In a recent study published in Cell, researchers have revealed for the first time the molecular mechanisms behind the unusual lifestyle of Corynebacterium. This breakthrough was made possible by the discovery of ways to genetically manipulate these bacteria, an advance that opens up a world of possible new research directions.
Nitin S. Baliga of the Institute for Systems Biology in Seattle said: "While metagenomics can tell us which microbes live on and in our bodies, DNA sequences alone do not give us insight into how beneficial or harmful they are. activity, especially for organisms that have never been characterized before. "
He added: "The ability to genetically disrupt Corynebacterium opens the possibility to apply a powerful systems analysis lens to rapidly characterize the unique biology of obligate periphyton." TAG PH20
The team behind the study was led by the laboratory of Joseph Mougous in the Department of Microbiology at Washington University School of Medicine and the Howard Hughes Medical Institute.
They are one of many unknown bacteria whose DNA sequences appeared in large-scale genetic analyzes of genomes discovered in species-rich microbial communities from environmental sources. This genetic material has been called "microbial dark matter" because so little is known about the functions it encodes.
The Cell paper points out that microbial dark matter may contain information on biochemical pathways with potential biotechnological applications. It also provides clues to the molecular activities that support microbial ecosystems and the cell biology of the various microbial species that assemble in this system.
The Corynebacterium analyzed in this latest study belongs to the Saccharibacteria group. They live in a variety of terrestrial and aquatic environments, but are best known for inhabiting the human mouth. They have been part of the human oral microbiome since at least the Mesolithic Age and have been implicated in human oral health.
In the human oral cavity, Saccharibacterium needs the companionship of Actinomycetes, which are their hosts. To better understand how yeast interacts with its host, researchers used genetic manipulation to identify all of the genes necessary for yeast to grow.
Mougous, professor of microbiology, said: "We are very excited to have a preliminary understanding of the function of the unusual genes carried by these bacteria. By focusing on these genes in the future, we hope to unravel the mystery of how glycobacteria use host bacteria to grow."
Possible host-interacting factors identified in the study include cell surface structures that may help Saccharibacterium attach to host cells, and specialized secretion systems that may be used to transport nutrients.
Another application of the authors' work is the generation of yeast cells expressing fluorescent proteins. Using these cells, the researchers performed time-lapse microfluorescence imaging of Saccharibacterium growing alongside host bacteria.
S. Brook Peterson, a senior scientist in the Moogers laboratory, noted: "Time-lapse imaging of Saccharobacterium-host cell cultures reveals the surprising complexity of the life cycle of these unusual bacteria."
The researchers report that some yeasts serve as mother cells, adhering to host cells and repeatedly budding to produce small progeny. These little guys continue to search for new host cells. Some offspring in turn become mother cells, while others appear to interact unhelpfully with their hosts.
The researchers believe that additional genetic manipulation studies will open the door to a broader understanding of the role of what they describe as "the rich reservoir of microbial dark matter harbored by these organisms" and potentially uncover biological mechanisms that have not yet been imagined.