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Fast Facts – Yellow Complex Bacteria

Fast Facts – Perio Edition Episode 5
[Andrew Johnston, RDH]
Welcome back,  everyone. You are listening to another episode of Fast Facts- Perio Edition brought to you by A Tale of Two Hygienists in partnership with DentistRX. And now, please welcome your host, Katrina Sanders.
[Katrina Sanders, RDH]
Hello and welcome to Fast Facts – Perio Edition. In this episode, we discuss the yellow complex bacteria as classified by Sokransky et al in their 1998 classifications. Previously we discussed green complex bacteria and the fact that although they do not create pathogenicity when it comes to periodontal disease, they absolutely have the ability to create other infections.
Today, we’re moving on to yellow complex bacteria, specifically the Streptococcal series, which comprises the largest species of the earliest colonizers. In these species we look at S. mitis, S. Oralis and S. sanguis.
Now, these early colonizers are typically obligate aerobics which means that they require oxygen based on their need to ferment or respire with the requirement of oxygen. Pulling in oxygen allows these bacteria to be able to generate more energy or ATP.
Typically they are gram positive, which means they stain purple, they are cocci, which means that they’re round. And although they are associated with gingival health, you’re going to learn in a moment that these particular colonizers have some abilities to invite the next layer of colonizers to the party.
These streptococcal species S. mitis, S. Oralis and S. sanguis adhere to the acquired pellicle.
These bacteria begin to release chemical signals that will eventually invite the next group of bacteria, encouraging a favorable condition for these orange and red complex bacteria to be able to join the colonization.
As biofilm continues to mature, as the acquired pellicle is laid down, as salivary glycoproteins allow for sticking of the green complex and then subsequently the yellow complex bacteria, we find that these early bacteria are unable to directly attach to the pellicle. However, these streptococcus series allow for easy co-aggregation, meaning cell to cell adherence. One bacteria is able to readily adhere to another bacteria.
And so, although these early colonizers may not have pathogenicity associated with periodontal disease, they provide chemical signals and easy adherence or attachment of next layers of bacteria to continue to allow the propagation of diseases of the periodontium. Stay tuned as we move forward in evaluating orange, red and pink complex bacteria.
This has been another episode of Fast Facts – Perio Edition with Katrina Sanders, RDH. Please feel free to reach me on Instagram @thedentalwinegenist or on my website Cheers.
[Andrew Johnston, RDH]
Thank you for listening to another episode of Fast Facts – Perio Edition, brought to you in part by DentistRX makers of the InteliSonic line of power brushes. Find out more by visiting their website at We’ll see you next week for another Fast Fact!

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