Strict host-symbiont cospeciation and reductive genome evolution in insect gut bacteria
Takahiro Hosokawa1, Yoshitomo Kikuchi, Naruo Nikoh
1Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.
Plos Biology
|October 13, 2006
Summary
This study reveals strict host-symbiont cospeciation in extracellular stinkbug gut bacteria, "Candidatus Ishikawaella capsulata," demonstrating reductive genome evolution previously seen only in endosymbionts.
Area of Science:
- Microbiology
- Evolutionary Biology
- Insect-Microbe Interactions
Background:
- Obligate endosymbiotic bacteria in insects often exhibit cospeciation and genome reduction.
- Extracellular insect symbionts have not previously shown these characteristics.
Purpose of the Study:
- To investigate host-symbiont cospeciation and genome evolution in extracellular symbionts of Plataspidae stinkbugs.
- To characterize the symbiotic bacterium and its transmission mechanism.
Main Methods:
- Phylogenetic analysis of symbionts and hosts.
- Experimental symbiont removal to assess host dependency.
- Genomic analysis of symbiont nucleotide composition and genome size.
Main Results:
- Strict cospeciation observed between Plataspidae stinkbugs and their gut symbionts, "Candidatus Ishikawaella capsulata."
- Symbiont removal led to host growth retardation, mortality, and sterility.
- Symbionts showed AT-biased composition, accelerated evolution, and reduced genome size, similar to endosymbionts.
Conclusions:
- Extracellular symbiosis can drive cospeciation and reductive genome evolution.
- Vertical transmission and population dynamics, not endocellularity, may explain these symbiotic genome traits.
- Plataspidae stinkbugs offer a model for studying insect-microbe mutualism and symbiotic genome evolution.
Related Concept Videos
01:15Diversity of Protists I
Excavata is a diverse group of protists that includes both chemoorganotrophic and phototrophic species, with some thriving in anaerobic environments. Among the key groups within Excavata are diplomonads and parabasalids, which are flagellated protists that lack mitochondria and chloroplasts. These microorganisms typically inhabit anoxic environments, such as the intestines of animals, where they exist either symbiotically or as parasites, relying on fermentation for energy production. Some...
01:08Evolution of Microbial Genome
Microbial genome evolution is a highly dynamic process shaped by continual gene gain and loss across species and strains. This genomic flexibility allows microorganisms to adapt rapidly to environmental pressures and interactions with other organisms. Central to understanding this diversity is the distinction between the core and pan genomes.The core genome comprises the genes shared by all sampled strains of a species, representing essential functions needed for fundamental cellular processes.
01:25Microbial Interactions: Mutualism
Mutualism is a symbiotic interaction in which all participating organisms benefit. These relationships can be obligate or facultative and are fundamental to ecosystem functions across diverse biological systems.Plant–Fungi MutualismOne well-known example is the association between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae penetrate the root hairs and the epidermis, forming an extensive hyphal network that establishes a symbiotic association. Through this...
01:26Microbial Interactions: Cooperation
Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...
01:22Microbial Interactions: Parasitism
Parasitism is a form of microbial interaction in which parasitic microbes exploit a host organism for nutrients and shelter, often at the host's expense. Unlike mutualistic relationships, where both organisms benefit, parasitism benefits only the parasite and harms the host.Classification of ParasitesMicrobial parasites are broadly classified based on their location relative to the host.Ectoparasites remain on the host’s surface, such as the skin or outer tissues, drawing nutrients...
01:27Microbiota of the Large Intestine
The large intestine hosts the most densely populated microbial ecosystem in the human body. This complex community primarily consists of anaerobic bacteria, with Bacillota (formerly Firmicutes) and Bacteroidota (formerly Bacteroidetes) as the predominant groups. The distribution of these microbes varies along different sections of the large intestine, influenced by local environmental factors such as oxygen availability and nutrient composition.The cecum, located at the beginning of the large...