Contemporary Microbiology Flashcards
how did the scientists first demonstrate that microorganisms play a role in dental caries?
They showed that bacteria in saliva could ferment carbohydrates (like sugars) into acids and the acids then demineralize the tooth surface, leading to caries formation (tooth decay).
what is the Non-specific plaque hypothesis ?
early theory that suggested any plaque with enough bacteria plus sugar exposure could cause caries.
**It didn’t focus on specific types of bacteria
what are the modern molecular techniques used to detect or confirm the presence of microbes?
Close-ended Techniques (detect only known targets):
- PCR
- DNA-DNA hybridization
- Reverse capture DNA-DNA hybridization
- Microarrays (HOMIM)
Open-ended Techniques (broad, exploratory)
- 16S rRNA sequencing
- Whole metagenome sequencing
- Whole metatranscriptome sequencing
how are bacteria cultured?
growing bacteria on:
- Non-selective media which allows growth of many different types of bacteria
- Selective or differential media: to highlight specific species
what are biochemical assays?
diagnostic tests performed after bacterial culture, in which isolated colonies are exposed to specific substrates or indicators to assess their metabolic and enzymatic activities allowing for the identification and differentiation of bacterial species
what was the Specific Plaque Hypothesis?
proposed that only certain bacterial species within the dental biofilm—primarily mutans streptococci, lactobacilli, actinomyces, and possibly non-mutans streptococci—were responsible for causing dental caries
What is the role of mutans streptococci in dental caries?
considered the most important etiological agents of dental caries, particularly responsible for the initiation of coronal carious lesions
How many serotypes of mutans streptococci are found in humans, and which species do they include?
8 known serotypes of mutans streptococci in humans: a–g and k
- Streptococcus mutans includes serotypes c, e, f, and k
- Streptococcus sobrinus includes serotypes d and g
what are the Virulence Factors of Mutans streptococci ?
- Acidogenic: ferment dietary sugars into lactic acid
- Acidouric: can survive in low pH environments
- Adhesion Abilities: Sucrose-dependent mechanisms and Sucrose-independent pathways
what are two major types of epidemiological studies used to understand microbial exposure and disease outcomes?
Association Studies
Risk Prediction Studies
what are Lactobacilli and what is their role in dental caries?
acid-producing (acidogenic) bacteria but are not strong colonizers of tooth surfaces due to low avidity (stickiness) therefore not usually involved in the initiation but are involved in the progression of carious lesions
what are the common Lactobacillus species found in the mouth?
L. fermentum
L. gasseri
L. rhamnosus
L. casei
L. paracasei
what carious lesions have lactobacilli been shown to play a major roll in?
progression of deeper carious lesions, particularly those extending into dentin due to being highly acidogenic and Aciduric
what role do Actinomyces play in dental caries?
root caries (questionable)
what role do Non-Mutans Streptococci play in dental caries?
in low levels of S. mutans they can take on a more active role in initiating or contributing to caries and carry acid production abilities
Examples of Non-mutans Streptococci:
Streptococcus mitis
Streptococcus intermedius
Streptococcus sanguinis
what is the ecological hypothesis?
dental caries result not simply from specific bacteria, but from a shift in the overall balance of the oral microbial community
examples of Actinomyces:
A. nauslundii I and II
what is the extended ecological hypothesis?
changes in the oral environment—especially the frequency and intensity of acid exposure—can shift the balance of oral bacteria and lead to caries
Candida albicans is a fungus that may play a role in
causing tooth decay, especially in young children because it can:
- Stick to teeth by forming biofilms
- Make acid from sugars (acidogenic)
- Survive in acidic environments (aciduric)
- Work together with Streptococcus mutans
how do Candida albicans and Streptococcus mutans work together?
help grow stronger biofilms, increasing glucan production and making dental plaque more harmful
what are the two types of PCR used to amplify DNA?
- Conventional PCR: Detects if a DNA sequence is present
- Real-time PCR (qPCR): detects DNA and measures how much is there
what is the DNA-DNA hybridization technique?
specific type of DNA hybridization used to compare the genetic similarity between two organisms by measuring how well their DNA strands bind to each other
what is the Human Oral Microbe Identification Microarray (HOMIM)?
a bacterial “fingerprinting” test for your mouth by checking which bacteria are present by matching their DNA to known bacterial DNA patterns
