Mesorhizobium loti

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Mesorhizobium loti

Classification

Higher order taxa

(Domain)Bacteria; (Phylum) Proteobacteria; (Class) Alphaproteobacteria; (Order) Rhizobiales; (family) Phyllobacteriaceae; (genus) Mesorhizobium; (species) loti) [Link for M. loti - use [1] NCBI link to find]

Species

Mesorhizobium loti

Description and significance

Though this bacteria was vaguely studied starting from the early 1880's it was finally sequenced by the Kazusa DNA Research institute in 2000. Rhizobia (from the Greek words rhiza = root and bios = Life) are soil bacteria that fix nitrogen (diazotrophy) after becoming established inside root nodules of legumes (Fabaceae). The rhizobia cannot independently fix nitrogen, and require a plant host. Morphologically they are generally gram negative, motile, non-sporulating rods.


Mesorhizobium loti is a member of rhizobia (rhizobia is a collective name for the genera of Rhizobium, Sinorhizobium, Mesorhizobium, and Bradyrhizobium). They are soil and rhizosphere bacteria which perform nitrogen-fixing symbiosis with leguminous plants. Nitrogen fixation reulsts from a series of interactions controlled by the exchange of molecular signals between symbiotic bacteria and host plants followed by expression of genes from both symbiotic partners.

Specifically, the Mesorhizobium species has the ability to form nodules and was studied in order to further understand the process of symbiotic nitrogen fixation as well as horizontal gene transfer among natural microsymbionts.


Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.

Genome structure

The complete nucleotide sequence of the genome of a symbiotic bacterium Mesorhizobium loti strain MAFF303099 was determined. The genome of M. loti consisted of a single chromosome (7,036,071 bp) and two plasmids, designated as pMLa (351,911 bp) and pMLb (208, 315 bp). The chromosome comprises 6752 potential protein-coding genes, two sets of rRNA genes and 50 tRNA genes representing 47 tRNA species. Fifty-four percent of the potential protein genes showed sequence similarity to genes of known function, 21% to hypothetical genes, and the remaining 25% had no apparent similarity to reported genes. A 611-kb DNA segment, a highly probable candidate of a symbiotic island, was identified, and 30 genes for nitrogen fixation and 24 genes for nodulation were assigned in this region. Codon usage analysis suggested that the symbiotic island as well as the plasmids originated and were transmitted from other genetic systems. The genomes of two plasmids, pMLa and pMLb, contained 320 and 209 potential protein-coding genes, respectively, for a variety of biological functions. These include genes for the ABC-transporter system, phosphate assimilation, two-component system, DNA replication and conjugation, but only one gene for nodulation was identified. Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen