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
We developed a new medium, designated peptone bile amphotericin cycloheximide (PBAC) agar, which contains (per liter) 10 g of peptone, 300 mg of bile salts, 1 mg of amphotericin B, 1 g of cycloheximide, and 15 g of agar. When 21 samples of fresh ground beef were studied and plate count agar counts were used as references, we obtained a mean recovery of 28% of total counts with violet red bile agar overlay, whereas we obtained 48% recovery with PBAC agar. With 12 samples of frozen ground beef, recovery on violet red bile agar overlay was 29% of the recovery on plate count agar, whereas the corresponding value on PBAC agar was 45%. PBAC agar allowed the enumeration of 1.4 times as many gram-negative bacteria as violet red bile agar overlay. None of eight strains of gram-positive bacteria and none of eight strains of yeasts grew on PBAC agar. Of 158 colonies randomly selected from pour plates of eight fresh ground meat samples, 95% stained gram negative. In comparison, only 70% of 151 colonies selected from corresponding plate count agar plates were gram negative. The lack of background color, turbidity, and ease of use make PBAC agar easier to handle than other media used for gram-negative bacteria, such as violet red bile agar, violet red bile agar overlay, and crystal violet tetrazolium agar. In the preparation PBAC agar, all ingredients are autoclaved together except amphotericin B, which is filter sterilized and added before the plates are poured.
When the endotoxin content of ground beef was determined by direct serial dilution and by three-tube most-probable-number methods, the results were not significantly different, although the latter method provided more specific values for individual samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.