Fastidious, gram-negative xylem-limited bacteria were examined for genetic relatedness to each other and to members of the major phytopathogen-containing genera of gram-negative bacteria. All of the xylem-limited bacterial strains studied had deoxyribonucleic acid base compositions of approximately 50.5 mol% guanine plus cytosine and genome molecular weights of 1.4 X lo9 2 0.2 X lo9. The results of our deoxyribonucleic acid-deoxyribonucleic acid hybridization experiments suggested that these strains are all related at the species level, but supported distinction at the varietal level, and possibly at the subspecies level between the bacteria causing Pierce's disease of grapevine and the bacteria causing phony disease of peach, plum leaf scald, and periwinkle wilt. No relatedness was detected between the xylem-limited bacteria and Erwinia chrysanthemi, Pseudomonas syringae pv. syringae, Xanthomonas campestris pv. campestris, or Agrobacterium tumefaciens.The significance of the recently discovered fastidious gram-negative xylem-limited bacteria (XLB) in plant diseases has become increasingly evident (8,15). XLB, also referred to as rickettsia-like bacteria, have been isolated from diseased plants, insect vectors, and apparently healthy reservoir plants (8,15,26), indicating a complexity of XLB-host-vector interactions. Studies on etiology (14, 15, 191, culture requirements (6, 8, 25), serology (7,12,20,22,26), and certain biochemical characteristics (15, 24) have indicated that the XLB are not related to the major phytopathogen-containing genera of gram-negative bacteria and can be subdivided into at least two closely related subgroups of unknown taxonomic distinction or affiliation.In this study, the relatedness of several XLB to each other and to other gram-negative phytopathogens was examined and defined by the following three criteria: deoxyribonucleic acid (DNA) base composition, genome molecular weight, and DNA homology.(The results were taken from a thesis presented by S.M.K. to Florida State University, Tallahassee.) MATERIALS AND METHODSBacterial strains and culture conditions. Two strains of the plum leaf scald bacterium, strains PLSB-40 and PLSB-53, and one strain of the phony peach disease bacterium, strain PPDB-2.1, were isolated by W. J. French at Monticello, Fla. (strains PLSB-40 and PPDB-2.1) or Cascata, Rio Grande do Sul, Brazil (strain PLSB-53). One strain of the Pierce's disease bacterium, strain PDB-1, was provided by N. W. Schaad, University of Idaho, Moscow, and one strain of periwinkle wilt bacterium, strain PWB-1, was provided by M. J. Davis, University of Florida, Ft. Lauderdale. Stationary cultures of strains PLSB-40, PLSB-53, PPDB-2.1, and PWB-1 in PW broth (8) and shaker cultures of strain PDB-1 in PD2 broth (10) were grown at 28°C for 5 to 7 days. Erwinia chrysanthemi A-17, Xanthomonas campestris B-24, Pseudomonas syringae C-7, and Agrobacterium tumefaciens 84G-102 were provided by N. W. Schaad, Escherichia coli K-12 C600 was provided by H. J. Taylor, Florida State * Corresponding aut...

The isolation of lysozyme from the egg white of several representative species of waterfowl is described. The purified lysozymes were analyzed to determine the type and molecular weight of each enzyme. All enzymes found in duck egg whites were found to be of the c-type. In contrast all true geese, and the mute swan species as well as the northern blackneck screamer contain lysozyme g in their egg white.

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