6.6 Microbial communities and Differentiation: Growth in nature

Biofilm:

Polymer-encased (matrix) community of microbes

1) Initial attachment and adherence of initial cells is important

2) Matrix helps provide protection

• antibiotics, host immunity, flow

3) Facilitates movement of nutrients and waste through channels

4) Can consist of more than one species, or domain

5) Pieces of biofilm can detach and spread

What is Biofilm made of?

Extracellular Polymeric substances (EPS) - polysaccharides, DNA

How is secretion of EPS regulated

Through Quorum Sensing

• high population or late log

Where is biofilm found? examples?

Abundantly found in nature and can grow on organic, living, or abiotic surfaces

• Includes tissue, teeth, and medical implants/devices

  • »70% of infections are in biofilm form

What does biofilm help?

microbes resist the immune system,

antibiotics, and disinfectants

Environmental biofilms

• Can be a nuisance (water pipes)

• or a benefit (bioremediation)

Some ______ bacteria produce differentiated cell form called an ______

Gram +; Endospore

What are endospores very resistant to

• Heat

• Chemicals

• Radiation

• Dehydration

Some can even exist for decades

*sometimes called the cell’s “resting” state

How are endospores formed?

Sporulation

• process cued by environmental conditions (usually starvation)

Germination

Process where endospore returns to Vegetative

Tyndall and Cohn

Discovered Endospores

~ 10 years and Pasteur’s S-Flask experiment

Dipicolinic Acid

• Produced in later stage of sporulation

• Stabilizes and protects spore DNA

• Stays hydrated, very heat stable

Sporulation process

Asymmetric division → Engulfment → Cortex formation → maturation, Spore release → Germination