Methylobacterium

Methylobacterium is a taxonomic genus of bacteria whose type species is Methylobacterium organophilum.^[ref] The 1976 genus description concerned pink, rod-shaped isolates and emphasized facultative methylotrophy: using one-carbon compounds while also being able to grow with more complex organic carbon sources. That is a description of the original isolates, not a promise that every bacterial strain subsequently assigned to Methylobacterium has identical physiology.^[ref]

Plant experiments show why identifying the genus is only a starting point. In 2011, researchers established candidate bacterial colonists on Arabidopsis thaliana, then tested their effects during challenge by Pseudomonas syringae pv. tomato DC3000. The tested Methylobacterium strains did not reduce disease development, whereas some Sphingomonas isolates did.^[ref]

The negative result distinguishes presence from protective function. Detecting a Methylobacterium sequence on a healthy leaf does not establish that the bacterium caused the leaf to remain healthy. Testing that idea needs a controlled comparison with a specified strain, host and outcome. Equally, failure to protect in this experiment does not rule out other interactions in different biological settings.

Methylobacterium radiotolerans is a species of bacteria within Methylobacterium. Its type strain has deposits including DSM1819, ATCC27329 and JCM2831. The organism was originally named Pseudomonas radiora; the accepted combination and corrected epithet place it in Methylobacterium. The epithet refers to tolerating radiation.^[ref]

A radiation-related name does not itself supply a survival curve. In an invented measurement, suppose a specified exposure leaves $2\times 10^5$ recoverable colony-forming units from an initially comparable $10^6$. The measured fraction is $2\times 10^5/10^6=0.2$, or 20 percent. Comparing organisms requires a stated bacterial strain, exposure and recovery readout; a single species adjective cannot fix those conditions or identify a universal resistance threshold. These numbers illustrate the measurement, not observed values for this species.

Reference-culture identity also matters when interpreting molecular data. LPSN notes that the older deposit DSM760, once associated with Methylobacterium organophilum, represents Methylobacterium radiotolerans.^[ref] A genome comparison based on an incorrect label could therefore attribute between-species differences to variation within one species. The name, maintained strain and measured phenotype are complementary pieces of a reproducible record.

Methylobacterium organophilum is a species of bacteria and the type species of Methylobacterium. Its reference strain is maintained under collection identifiers including ATCC27886, DSM18172 and NBRC15689. These codes identify deposits of the reference material, rather than three different species.^[ref]

The organism provides a concrete example of why provenance matters in genome comparisons. A 2021 comparative study newly sequenced the NBRC15689 reference strain because an existing assembly attributed to an older deposit, DSM760, did not reliably represent the intended taxon. LPSN identifies DSM760 as Methylobacterium radiotolerans.^[ref][ref] An internally well-assembled sequence can therefore still answer the wrong biological question if its source organism is misidentified.

For a comparison example, imagine two reports carrying the same species label, one based on the intended reference culture and one on a misassigned culture. A difference in gene content could arise from the identity mismatch rather than from ordinary variation within the species. Resolving the strain's collection code and biological identity must precede that interpretation. The lesson links naming, preserved cultures and sequence measurements: each supplies information needed to make the others scientifically reusable.