Application of Polyacrylamide Gel Electrophoresis to the Characterization and Identification of Arthrobacter Species

Abstract

When polyacrylamide gel electrophoretic profdes of soluble proteins of seven Arthrobacter strains were compared with those of seven coryneform and coryneform-like species, the arthrobacters were delineated from the latter species. Comparisons were made from a composite gel by calculating similarity coefficients. When Arthrobacter globifomis was used as a reference, similarity coefficients for the other Arthrobacter species ranged from 20.7 to 34.5, but the similarity coefficients for the other genera tested were only 7.9 to 18.5. In addition to a separation of arthrobacters from other corynefonns by this method, Arthrobacter crystallopoites and Arthrobacterpyridinolis had a similarity coefficient of approximately 95, which set these two apart from the other Arthrobacter species studied and furthermore suggested that they represent one species. Gel electrophoresis of soluble proteins may provide a good alternative to the use of rod to coccoid transition for identifying arthrobacters since it is faster and simpler to perform than chemical analyses of cell wall components.Arthrobacters are aerobic, nonsporefonning, gram-positive bacteria which change morphology during growth from pleomorphic rods when young to coccoids as they age. Because the genus description is based on this morphological cycle (3), there is confusion about the taxonomy of Arthrobacter and related genera, some of which exhibit less pronounced life cycles. The genus Arthrobacter is included in the coryneform group, which includes three other genera according to Bergey' for seven genera of coryneforms based on principal cell wall amino acids, mode of division, deoxyribonucleic acid composition, and biochemical and physiological characteristics. Their scheme for dividing coryneform genera indicated that many strains may have been improperly identified. The methods employed by these investigators are time consuming at best. More recently, Stackebrandt and Fiedler (9) studied deoxyribonucleic acid-deoxyribonucleic acid homologies among 16 strains of Arthrobacter and found a homology range between 11 and 55% to the type strain of the type species, A. globifomis ATCC 8010. For two strains of A. globifomis tested, a homology of only 30% was found. These findings emphasize the need for a better understanding of the taxonomic relationships of the coryneforms in general and the arthrobacters in particular.Therefore, it was the aim of this study to investigate the use of polyacrylamide gel electrophoresis for differentiating arthrobacters from other corynefonns on the basis of their soluble protein fractions and to assess the efficacy of employing this method in the routine identification of arthrobacters. MATERIALS AND METHODS Bacterial

Numerical Analysis of Normalized Whole-cell Protein Profiles after Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis

“…This is especially evident with the phosphorylase B and bovine serum albumin standards. The CVs for the RF values confirm the observations of other authors who question the stability of RF values within and among gels (Seiter & Jay, 1980). The CVs for the RF values tend to be of the same magnitude as the CVs for the actual migration distances and are, in all cases but one, larger than those of the normalized migration distances.…”

“…Kersters & De Ley (1980) reported that electrophoregrams (scans of protein banding patterns or profiles) of bacterial strains produced under well-defined and standardized conditions can be considered unique and that genetically closely related bacteria display similar or almost identical electrophoregrams. However, experimental variability in factors associated with gel electrophoresis precludes the comparison of absolute migration distances among gels (Seiter & Jay, 1980). Many investigators standardize or normalize the migration distances of the protein bands by computing RF values, i.e.…”

“…the ratio of the migration distances of the protein bands to that of a tracking dye at the bottom of the gel (Hames, 1981). However, RF values are nonreproducible in common practice, and they do not completely eliminate the variability of the protein band positions within gels (Seiter & Jay, 1980;Chrambach et al, 1976). Kersters & De Ley (1975 and Kersters (1985) incorporated two internal standards in each sample preparation to normalize the resulting protein band migration distances, thus facilitating gel-togel comparisons of electrophoregrams.…”

“…Kersters & De Ley (1975 and Kersters (1985) incorporated two internal standards in each sample preparation to normalize the resulting protein band migration distances, thus facilitating gel-togel comparisons of electrophoregrams. Additional techniques involve the inclusion of reference or type strains on each gel to normalize the remaining profiles on that gel (Seiter & Jay, 1980), but it is unclear to what extent this approach reduces the intragel variability.…”

Polyacrylamide Gel Electrophoresis of Whole-Cell Preparations of Actinomyces spp.

“…PAGE of soluble proteins can be used to differentiate closely related bacteria (1,11,13,17) and has been used to show differences among strains of Actinomyces spp. (7, 8 , 13).…”