The oral bacteriome comprises about 700 species, most of them anaerobic and participating in symbiotic relationships with their human host and each other which are essential for overall health, not just of the mouth but also of the heart, the brain, and other organ systems. Up to one third of these bacteria have been characterized solely by culture-independent molecular methods such as 16S rRNA cloning, but have yet to be cultivated in vitro. These bacteria are so difficult to culture outside of their biofilm habitat because they rely on metabolic cooperation and intercellular signaling with the community.
Sonia Vartoukian and William Wade of Queen Mary University of London, using their Don Whitley Scientific anaerobic workstations, have been shining a bright light into the dark niches of the oral cavity for years. They have identified a novel species in a new genus, Fretibacterium fastidiosum, through co-culture with other oral bacteria cultured in the anaerobic workstation. More recently, they were able to isolate five novel strains from subgingival plaque, using a combination of community culture with helper strains and supplementation with siderophores as growth supplements. The bacteria are surprisingly agile in adapting to changes in their co-dependent habitat, as long as they are provided with the signals and factors they themselves have lost the ability to synthesize. Over the course of up to 21 day culture of the samples, Vartoukian and Wade were fastidious about not exposing the cultures to air, using plates that were pre-reduced in the workstation’s anaerobic atmosphere and making sure to minimize time spent outside of the workstation.
On the other side of the Atlantic, Microbiology International distributes the Don Whitley Scientific anaerobic workstation to North American groups researching the oral bacteriome in physiology and disease. Dr, Yihong Li at New York University Department of Dentistry uses her A35 workstation “to facilitate cutting-edge research in clinical microbiology, antimicrobial treatment evaluation, and infectious disease identification”. The A35 can accommodate up to 600 90 mm plates and features bare-handed access to a consistent and strictly anaerobic environment, reliably monitored by the Anaerobic Conditions Monitoring System. Dr. Li’s research on dental caries has shown that the anaerobic environment is essential for colonization by oral lactobacilli. Her group’s large-scale studies of the diversity of lactobacilli associated with severe early childhood caries have demonstrated the necessity to provide a range of anaerobic and microaerophilic niche environments in order to capture the complexity of Lactobacillus variables.
Dr. Wade of the University of London says of the anaerobic workstations he has been using since the early 1980’s, “The Don Whitley Scientific workstations have been invaluable for our work characterising the human oral microbiome. Many oral bacteria are highly sensitive to oxygen and extremely slow-growing and thus need long incubation times which are possible in the controlled atmosphere and humidity of the workstations. Hands-free working has also allowed us to work with precision inside the workstation and process samples and prepare culture plates in the anaerobic atmosphere. Use of the workstations has allowed us to culture numerous previously uncultivated oral bacteria. This has made a substantial contribution to our Human Oral Microbiome Database (www.homd.org) which is a reference resource for oral bacteria and includes over 400 bacterial genome sequences, many of which are for strains which have been isolated by our group.”