Actinobacterial Diversity and Dynamics as Revealed by Denaturing Gradient Gel Electrophoresis

Abstract

The microbial consortia from red smear cheeses is poorly defined and often biased by culture dependent approaches. A reflection of the true diversity of the surface microflora is necessary to enable the selection of strains which generate the colour, aroma and organoleptic qualities of specific cheeses and to screen for anti-listerial activity. Following the advent of molecular ecological techniques it has become clear that isolation techniques give a biased view of community composition, often missing dominant members of the community and isolating rapidly growing but numerically insignificant strains. In this study identification of the smear flora using molecular techniques revealed immense diversity not known before. Denaturing gradient gel electrophoresis (DGGE) was applied as a high throughput screening strategy to reveal the diversity and dynamics from three stages of ripening of four different European smear cheeses. A combined approach of cloning with DGGE gave similar results showing the robustness of the method. The molecular analysis revealed different complex patterns of bands for each cheese, and changes with ripening stage. Most of the species revealed by molecular analysis using DGGE and sequencing were similar to recognised species of Brevibacterium, Corynebacterium and Microbacterium. Some unexpected species were detected such as Citrococcus and Propionibacterium. The study provided a comprehensive overview of the actinobacterial flora present on red smear cheeses and provides the source information for the future study of anti-listerial properties and to develop defined inocula.