Host factor for coliphage Qbeta RNA replication as an aid in elucidating phylogenetic relationships: the genus Pseudomonas

Host Factor (HF) is a heat-stable RNA-binding protein required along with Qbeta replicase for in vitro transcription of coliphage Qbeta RNA. We have found that HF activity and antigenicity are conserved among certain Gram-negative bacterial species. We examined selected species within the genus Pseudomonas for the presence of the HF polypeptide's antigenicity and Qbeta RNA replication function. While we were unable to detect either of these in Pseudomonas diminuta or Pseudomonas vesicularis, the other eleven species tested contained cross-reacting material to Escherichia coli HF. Furthermore, in six of these eleven species we were able to detect HF activity. The detection of HF structure and function allowed the examined species to be grouped into three categories which we have called 'sets'. The results correlate well with those of previous studies on ribosomal RNA homology (Palleroni et al., 1973).