34 - Microbial interactions

Question 1

Oral Eubiosis

Answer 1

Microbial balance within the oral cavity

Question 2

Oral Microflora

Answer 2

• Can be resident/transient
• Acquired from saliva, food + H20

It can also cause various diseases:

• abscesses
• dental caries
• gingivitis
• periodontal diseases

Question 3

Interactions

Answer 3

• Interspecies collaboration
• Interspecies competition
• Interspecies communication
• Collaborative invasion
• Bacterial co-aggregation
• Microbial relationship

Question 4

Interspecies collaboration

Answer 4

Some anaerobic species such as P.gingivalis need a co-aggregation to survive in the presence of oxygen

Question 5

Interspecies competition

Answer 5

Many oral species produce substances that kill closely related competitors

eg. Wild type S.mutans

Question 6

Interspecies communication

Answer 6

Bacteria sense other species based on their characteristics

Eg. Streptococci ferment CHO + excrete lactic acid ⇢ Veillonella uses lactic acid for nutrition

Question 7

Collaborative invasion

Answer 7

F.nucleatum invades epithelial cells but S.Cristatus cannot

After co-aggregation ⇢ S.Cristatus is carried inside by F.nucleatum

Question 8

Bacterial co-aggregation

Answer 8

Process that helps in development + maintenance of mixed-species biofilm communities

Question 9

Microbial relationship

Answer 9

Complex of relations between microbial species:

• Neutral ⇢ between 2 species that live together without affecting the other
• Synergy ⇢ Between 2 species living together + both mutually favoured
• Antagonism ⇢ Between 2 microbes living together + yielding inhibition of their function

Question 10

Bacterial plaque

Answer 10

Subgingival plaque

• G- only
• In tooth’s sulcus

Subgingival plaque

• On approximal, occlusal + cervical surfaces
• Main species ⇢ Facultative anaerobes (S. Actinomyces) + G- (Veillonella, Haemophilus)

Question 11

!!!Note!!!

Answer 11

Oral microflora varies between people

Biofilm

• Initiated by bacterial adhesion to surface
• Occurs when bacteria attaches to surface + excretes exopolymer
• Exopolymer ⇢ imbeds bacteria + attracts other microbes to newly formed microfilm

Oral plaque = main biofilm in mouth

• Attracts high concentration of bacteria
• Leading to oral diseases