Module 5: Section 1B

Question 1

Species Complexity in Biofilms

Answer 1

• Biofilms form when microbes shift from free-floating (planktonic) to attached (sessile) forms
• They often contain many microbial species living together, creating complex, multispecies bacterial communities common in natural environments

Question 2

Mixed Species Biofilm Formation

Answer 2

• Bacteria form mixed-species biofilms using quorum sensing, where they communicate through signaling molecules like Autoinducer-2 (AI-2)
• This allows both intraspecies and interspecies communication, coordinating biofilm development across different microbes

Question 3

Process of mixed species biofilm formation - step 1

Answer 3

• Initially, commensal organisms begin to form a biofilm
• Number of bacteria is low, so the amount of AI2 secreted is low
• Intraspecies communicates requires low concentrations of AI2
• Leads to mutual benefits that enhance growth

Question 4

Process of mixed species biofilm formation - step 2

Answer 4

• As bacteria accumulate, AI2 levels increase until they reach a level that can be sensed by pathogens
• Pathogens are then attracted to the biofilm and incorporated into it, eventually building a layer of plaque

Question 5

From Bacteria to Barnacles

Answer 5

Bacterial biofilms in aquatic environments act as food sources or attachment sites for other organisms like barnacle larvae

Question 6

Biofouling and Marine Equipment

Answer 6

• Biofouling occurs when biofilms and organisms (like barnacles) attach to marine equipment or ship hulls, causing increased drag, corrosion, and fuel use
• It can also lead to species being transported to new environments through global ship travel

Question 7

Biofilms on Medical Devices

Answer 7

• Biofilms can quickly form on indwelling devices like catheters and stents, leading to blockages and infections
• These bacterial biofilms reduce flow and make devices harder to sterilize

Question 8

Bacterial Streamers in Biofilms

Answer 8

• Streamers are a key feature of biofilms found in natural, industrial, and medical environments
• They can form in places like bare-metal stents and significantly disrupt fluid flow

Question 9

Medical Importance of Streamers

Answer 9

In ureteral and biliary stents, streamers clog flow more severely than wall-attached biofilms, creating serious challenges for medical device use in non-sterile environments