Comparisons between two Klebsiella: The plant endophyte K. pneumoniae 342 and a clinical isolate, K. pneumoniae MGH78578

Bacterial strains of potential value to agriculture that promote plant growth or control plant disease are often close relatives of isolates associated with human disease. Klebsiella pneumoniae endophytes isolated from maize, Kp342, Kp2028, and Kp zmvsy are examples of this dilemma. These strains enhance plant growth and are endophytes of a wide variety of plant species. This work represents a collection of experiments to define the taxonomic status of these endophytes and to compare several phenotypes of this strain to a clinical isolate, K. pneumoniae MGH78578 (KpMGH). Three genetic assays show that although the maize endophytes are members of K. pneumoniae they are more closely related to each other and to the type strain of the species (Kp13883) than they are to KpMGH. In addition, the endophytes lack the complete set of virulence factors assays that are present in KpMGH. Most physiological and metabolic characteristics were shared by all strains further confirming the identity of these endophytes as K. pneumoniae. However, the maize endophytes colonized the interior of wheat seedlings in much higher numbers than either KpMGH or Kp13883. These results show that these endophytes are strains of K. pneumoniae but they are distinct from a clinical isolate.