This study compares MATERIALS AND METHODSWe determined minimum inhibitory concentrations (MICs) by agar dilution by the procedure of Washington and Barry (9).Preparation of inoculum. Aerobic, gram-negative bacilli isolated by the Duke Clinical Microbiology Laboratory were streaked on nutrient agar (Difco Laboratories) to provide single colonies. After incubation and inspection for purity, plates were held at 4°C until used. Approximately five colonies were touched with a bacteriological loop and inoculated into tubes containing 2 to 5 ml of tryptic soy broth, which were incubated at 350C in air for 2 to 5 h. Turbidity was adjusted to that of a 0.5 MacFarlane standard by addition of further tryptic soy broth, the suspension was blended in a Vortex mixer, and a final dilution of 1:20 was made in tryptic soy broth. Plates were inoculated with a Steers replicator within 30 min of standardizing the inoculum. This method delivered approximately 104 colony-forming units CFU of each organism to the plates.Preparation of agar plates. LY127935 assay powder was supplied by Lilly Research Laboratories, cefoperazone was supplied by Pfizer, cefotaxime was supplied by Hoechst-Roussel, and thienamycin was supplied by Merck Sharp & Dohme. Cefoperazone and cefotaxime were dissolved in sterile, deionized water, LY127935 was dissolved in 0.1 M phosphate-buffered saline (PBS; pH 7.0), and thienamycin was dissolved in 0.01 M PBS. To make plates containing twofold dilutions, antibiotics were prepared in 50-ml, screwtopped tubes so that each held a final volume of 2.5 ml that contained 10 times the concentration of antibiotic required in each agar plate. A 22.5-ml amount of Mueller-Hinton agar from a single batch (control no. 656889) at a concentration of 1.5% at 50 to 550C was added to each tube to give a final volume of 25 ml. Antibiotic and agar were mixed by gentle inversion of the tube, which was then emptied into a 100-mm petri dish. Final concentrations of antibiotics in agar ranged from 64 jig to 0.03 ,ug of thienamycin. To test swarming Proteus, agar was prepared at a 3% concen-

The extant species of possums and gliders (Marsupialia : Diprotodontia) can be classified into one or other of six families-Acrobatidae, Phalangeridae, Burramyidae, Petauridae, Pseudocheiridae or Tarsipedidae. On the basis of morphological and albumin serology studies, these families have been assigned to two superfamilies: the Phalangeroidea (Phalangeridae) and the Petauroidea (all five other families). It has been suggested, however, that the Burramyidae should be placed in the superfamily Phalangeroidea and not in the Petauroidea. We report here on DNA-DNA hybridisation comparisons using representatives from all six extant families of possums and gliders. Phylogenetic analysis of these data was unable to resolve the precise relationships of the Burramyidae viz a viz other families, but the family appeared to be no more closely related to the Phalangeridae than to the four other families. The Burramyidae would probably be best assigned, at present, to a third superfamily. The radiation of the possum and glider families appears to be linked to the change in vegetation associated with the separation of Australia from Antarctica in the early-to-mid Eocene.

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Apex and Gophee are mycobacteriophages directly isolated from soil using the host Mycobacterium smegmatis mc2155. Apex has a 71,244-bp double-stranded DNA (dsDNA) genome encoding 98 putative proteins, and Gophee has a 68,556-bp dsDNA genome encoding 101 putative proteins.

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