Lecture 2.3 Notes

Lecture 2.3 Notes - The bacterial endospore d ifferentiated...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
2/3/10 The bacterial endospore – differentiated cells that are resistant to a wide variety of environmental insults (e.g. extremes of temperature, dessication, nutrient deprivation) Endospore-forming bacteria commonly found in soil true endospore found only among gram-positive bacteria: Bacillus and Clostridium best studied examples o other types of sporulation found among different species of bacteria but these are not as environmentally resistant as the endospore Cellular differentiation of vegetative cell into endospore Response to nutrient deprivation Development of environmentally-resistant resting cell Endospore structure: strongly refractile structures in light microscope Exosporium – outermost layer, thin protein covering Spore coats – layers of spore-specific proteins Cortex – loosely x-linked peptidoglycan Core (spore protoplast) Core wall Cytoplasmic membrane Cytoplasm – pH: 5.5 - 6 Ribosomes Nucleoid Dipcolinic acid Small acid-soluble proteins (SASPs) – bound tightly to DNA Mediate transition from B-form to A-form (more compact) Catabolized upon germination Dipicolinic acid spore-specific compound found in all endospore-forming bacteria Ca++-DPA complexes make up 10% of dry weight of cell Dehydration agent
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Spores contain 10-25% the water content of vegetative cell cytoplasm gel Intercalated into DNA and stabilizes against heat denaturation Well characterized process in B. subtilis Entire process completed within 8 hrs Genetic studies indicate involvement of >200 genes Developmental program – many vegetative functions turned off; spore- specific functions turned on Germination; Endospore can remain dormant for many years (report of endospores from gut of insect encased in amber: germination after 25-40 million years!!) Rapid conversion back to vegetative cell when conditions are right Activation – elevated by sub-lethal temperature in nutrient-rich environment Germination – proceeds rapidly (several minutes) Loss of Ca++-DPA complexes loss of cortex Degradation of SAPs Outgrowth Water uptake w/visible swelling New RNA, DNA and protein synthesis Emergence from broken cell coat Cell division How long can spores remain viable?? Report of
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 7

Lecture 2.3 Notes - The bacterial endospore d ifferentiated...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online