Stability of the Biodiversity of the Surface Consortia of Gubbeen, a Red-Smear Cheese

A total of 1,052 bacteria and 828 yeasts were isolated from the surface flora of 6 batches of Gubbeen cheese made in 1996-1997 and 2002-2003. Stability of the microflora was evaluated over time and also during ripening at 4, 10, and 16 d (batches 4, 5, and 6) or at 4, 16, 23, and 37 d (batches 1, 2, and 3). Bacteria were identified using pulsed-field gel electrophoresis, repetitive extragenic palindromic-PCR, and 16S rRNA gene sequencing, and yeasts were identified by Fourier transform infrared spectroscopy. The bacteria included at least 17 species, of which the most common were Staphylococcus saprophyticus (316 isolates), Corynebacterium casei (248 isolates), Brevibacterium aurantiacum (187 isolates), Corynebacterium variabile (146 isolates), Microbacterium gubbeenense (55 isolates), Staphylococcus equorum/cohnii (31 isolates), and Psychrobacter spp. (26 isolates). The most common yeasts were Debaryomyces hansenii (624 isolates), Candida catenulata (135 isolates), and Candida lusitaniae (62 isolates). In all batches of cheese except batch 2, a progression of bacteria was observed, with staphylococci dominating the early stages of ripening and coryneforms the later stages. No progression of yeast was found. Pulsed-field gel electrophoresis showed that several different strains of the 5 important species of bacteria were present, but generally only one predominated. The commercial strains used for smearing the cheese were recovered, but only in very small numbers early in ripening. Four species, B. aurantiacum, C. casei, C. variabile, and Staph. saprophyticus, were found on all batches of cheese, but their relative importance varied considerably. The results imply that significant variation occurs in the surface microflora of cheese.