Biomedical subjects
L M Swaney
Publications and source records attributed to L M Swaney.
Isolation and characterization of Escherichia coli phase variants and mutants deficient in type 1 pilus production.
Type 1 pili of Escherichia coli are the prototype of the somatic class of pili found on many strains of bacteria. As a first step in the genetic analysis of type 1 piliation, an extensive series of nonpiliated derivatives of E. coli K-12 strain AW405, was characterized to produce attached or free pili when examined in the antiserum or appeared to produce attached or free pili when examined in the electron microscope. The derivatives fell into two classes; phase variants and mutants. Phase variants that formed colonies of two distinctive types, one associated with a predominantly piliated (P+), and the other associated with a nonpiliated (P-) phase, were obtained. Each phase could give rise to the other at a relatively high rate, which was greater in the P- to P+ direction during culture in unshaken liquid medium. In addition, 77 Pil- mutants were selected on the basis of a subtle difference in colonial morphology. The mutants reverted, if at all, at a much lower rate than that of the P- to P+ change. The stability of Pil- derivatives grown in unshaken liquid medium was used as a criterion for distinguishing between phase variants and mutants, Phase variation also effected colonial morphology and chemotactic swarming. These properties did not directly depend upon piliation since Pil- mutants were only slightly altered in colonial form and unaltered in chemotactic swarming. Piliation of Pil+ bacteria was quantitatively affected by growth conditions.
Genetic complementation analysis of Escherichia coli type 1 somatic pilus mutants.
A genetic complementation analysis of 75 stable nonpiliated mutants of a type 1 piliated strain of Escherichia coli K-12, AW405, was performed. Strains containing pairs of pil mutations were constructed by the infectious transfer of an F101 plasmid containing one pil mutation into E. coli K-12 AW 405 containing another pil mutation. The presence or absence of type 1 pili on the merodiploid strains was determined by agglutination with type 1 pilus antiserum. All 75 mutants fell into one of four complementation groups. The pattern of complementation defined three cistrons involved in pilus formation, pilA, pilB, and pilC. The fourth complementation group was composed of a large number of mutants defective in both pilA and pilB functions.
Selection of a stable clone of the MVPK-1 fetal porcine kidney cell for assays of foot-and-month disease virus.
The MVPK-1 cell line, derived from fetal porcine kidney cells, supports the replication of foot-and-mouth disease (FMD) virus. The cell line was adapted to grow in medium containing 5% bovine serum. The susceptibility of the adapted cells decreased as they aged at 37 degrees C. Various clones were isolated from the adapted cells and their growth characteristics and sustained susceptibility to FMD virus were compared. Clone 7 maintained uniform susceptibility to FMD virus over a 3-day period at 37 degrees C and proved superior to other clones in the characteristics studied. The clone has maintained satisfactory susceptibility to FMD virus through 40 subcultures. Clone 7 can replace primary bovine kidney cells for routine viral assays, but cannot detect as much FMD virus in animal specimens as primary bovine kidney, bovine thyroid, or swine kidney cells.
Susceptibility of a new fetal pig kidney cell line (MVPK-1) to foot-and-mouth disease virus.
The Mengeling-Vaughn Porcine Kidney (MVPK-1) cell line, derived in October, 1970, from fetal pig kidneys, is susceptible to all 7 types of foot-and-mouth disease (FMD) virus. A plaque assay was developed for FMD virus that depended on washing MVPK-1 cells in serum-free medium before infection and excluding serum from 0.6% gum tragacanth overlay during plaque formation. The numbers of plaques that formed on MVPK-1 cells by a representative strain of each FMD type were comparable with the numbers of those on primary bovine calf kidney (BK) cells. Virus passaged in BK cell cultures did not have to be adapted to the cell line to obtain these results. The cell line lost susceptibility rapidly at 37 C after confluency was reached but retained susceptibility if maintained at room temperature. The cell line has the potential of replacing BK cells for many diverse purposes.