Isolation and characterization of mycoplasma virus L3 temperature-sensitive mutants

Mycoplasma virus L3 virions are morphologically similar to coliphage T7, contain linear double-stranded DNA of about 39 kilobase pairs, and produce a nonlytic cytocidal infection in Acholeplasma laidlawii host cells. Following nitrous acid mutagenesis, ninety-eight L3 temperature-sensitive (ts) mutants were isolated from a total of 57,000 plaque-forming units (PFU), using 37 degrees C as the permissive temperature and 41 degrees C as the nonpermissive temperature, with reversion frequencies of 10(-5) to 10(-8). Complementation tests allowed fifty-seven of the L3 ts mutants to be placed into twenty-one complementation groups. In mixed infections, recombination frequencies between mutants in different complementation groups were 10(-2) to less than 10(-6). Studies of protein synthesis in L3-infected cells showed synthesis of about twenty virus-specific proteins, including ten L3 virion proteins. After infection with L3 ts mutants from each complementation group, several different patterns of cell- and virus-specific protein synthesis were observed.