Appendix
Grouping of Gram-Positive and
Gram-Negative Bacterial Genera
Grouping of the genera of Gram-positive and Gram-negative bacteria is based on four phenotypic
characters: Gram reaction (GP = positive; GN = negative), oxidase (+ or −), catalase (+ or −), and
absence (n) or presence (p) of colony pigmentation. Groupings for most aerobic foodborne bacteria
can be made within 24–48 hours after surface plating onto plate count agar with incubation at 30
◦ C.
Foodborne and environmental bacterial genera are not known for the following two groups: GP 3 (Gr +
Ox + Cat − n) and GP 4 (Gr + Ox + Cat − n). Among Gram negatives, the genera in GN 3 (Gr −
Ox + Cat − n) and GN 4 (Gr − Ox + Cat − p) are rarely if ever reported in foods.
Gram-Positive Groups
GP 1: Gr + Ox + Cat + n
GP 2: Gr + Ox + Cat + p
Alicyclobacillus
Arthrobacter
Aneurinibacillus
Bacillus (some)
Arthrobacter
Brachybacterium
Bacillus (some)
Brevibacillus
Brachybacterium
Brevibacterium (some)
Brevibacillus
Corynebacterium
Brochothrix
Deinococcus
Corynebacterium (some)
Dermacoccus
Dermacoccus
Exiguobacterium
Geobacillus
Halobacillus
Gracilibacillus
Janibacter
Janibacter
Kocuria
Macrococcus
Luteococcus
Micrococcus
Macrococcus
Nesterenkonia
Micrococcus
Paenibacillus
Nesterenkonia
Propioniflex
Salinococus
Salibacillus
Streptomyces (most)
Sporosarcina
Staphylococcus lentus,
747