RT Journal Article SR Electronic(1) A1 Dubow, Michael S. A1 Ryan, ThomasYR 1977 T1 Host Factor for Coliphage Qβ RNA Replication as an Aid in Elucidating Phylogenetic Relationships: The Genus Pseudomonas JF Microbiology, VO 102 IS 2 SP 263 OP 268 DO https://doi.org/10.1099/00221287-102-2-263 PB Microbiology Society, SN 1465-2080, AB Host Factor (HF) is a heat-stable RNA-binding protein required along with Qβ replicase for in vitro transcription of coliphage Qβ 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 Qβ 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 )., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-102-2-263