= Methylobacterium
{c}
<Methylobacterium> is a <taxonomic genus> of <bacteria> whose <type species> is <Methylobacterium organophilum>.<Methylobacterium in LPSN>[Genus record, nomenclatural status and type species]{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.<Methylobacterium, a New Genus of Facultatively Methylotrophic Bacteria by T. E. Patt and others>[Abstract, original isolates and carbon-source comparison]{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.<Protection of Arabidopsis thaliana against leaf-pathogenic Pseudomonas syringae by Sphingomonas strains in a controlled model system by Gerd Innerebner and others>[Abstract and Figure1, Methylobacterium comparison]{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.
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