Sporulation in bacteria.pptx

Sporulation is the process of spores formation by bacteria during unfavorable condition
Germination is the process of spores return to give vegetative cells under favorable condition.

1. Microbiology Lecture sporulation and germination Instructor: Dr. Sulaiman A. Alqaesi University Of Anbar College of Pharmacy

2. Contents What is bacterial spore. Why was bacterium tend to convert into spore. What is spore structure. Shape and location of endospore. Mechanism of sporulation and germination. Medical Importance of Bacterial Spores. 15 June 2022

3. Introduction Bacteria have two phases life cycle: Vegetative cell – Metabolically active and growth. Bacterial spore - metabolically dormant structure, high resistance to sever conditions and very long-term survival, reach to millions of years. Sporulation is the process of spores formation by bacteria during unfavorable condition Germination is the process of spores return to give vegetative cells under favorable condition. 15 June 2022

4. Endospore Endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Firmicutes like Bacillus and Clostridium when exposed to sever environmental conditions like nutrition starvation. An endospore is: Hardiest of all life form. Resistance to heat, drying, freezing, radiation, extreme pH, antibiotics and chemicals. Not a mean of reproduction. Destroys by pressured steam at 120 o C for 20-30 minutes. 15 June 2022

5. Structure of endospore 15 June 2022 Inner membrane: Lipid, protein Spore coat: proteins Outer membrane: Lipid, protein Germination receptors GRs Exosporium: proteins Germ cell wall: peptidoglycan Core: DNA, RNA, Ca 2+ , DPA (Dipicolinic acid), SASPs (small acid-soluble spore proteins) Cortex: Modified peptidoglycan

6. Structure of endospore 15 June 2022 An endospore has following layers: 1. Exosporium 2. Spore coat 3. Cortex 4. core Exosporium: is the outer layer made up of protein that encloses spore coat. In some bacterial spore, exosporium is made up of polysaccharide and lipid. Spore coat: is thick double layered that encloses cortex. Spore coat consists of specific protein, mainly contains cysteine and hydrophobic amino acids. Due to presence of these amino acids, spore is resistant to adverse environmental condition. Cortex: is made up of loosely arranged peptidoglycan layer. it can be hydrolyzed during spore germination. Core: is the inner part of spore contains (10-25%) water so, the cytoplasm is gel like. It consists of core wall, cytoplasmic membrane, cytoplasm, nucleic acid, ribosomes and other cellular materials. It contains high amount of calcium and Dipicolinic acid which play a role in the heat resistance of bacterial endospores . Core also contains high percentage of small acid soluble protein (SASP), which is synthesized during sporulation and it binds to DNA in core and protect it from potential damage caused by UV radiation and drying. In addition, SASPs also provides nutrition and energy for spore germination.

7. Shape and location of endospore The shape and location of bacterial spore are characteristic of the different sporulating strains and can be used as distinguishing features. 15 June 2022 1 4 5 6 7 3 2 Terminal spherical endospore Sub-terminal spherical endospore central spherical endospore. Terminal oval endospore Sub-terminal oval endospore central oval endospore lateral endospore

8. Examples of spore forming bacteria 15 June 2022 Clostridium tetani with terminal spherical endospore (drum-stick-shape) Clostridium botulinum with Sub-terminal oval endospore clostridium perfringens with Sub-terminal oval endospore Bacillus spp. In chain with central spherical endospore

9. Sporulation or sporogenesis 15 June 2022 During unfavorable condition, vegetative cell converts into spore. The one vegetative cell forms a single spore. It takes 8 to19 hrs to complete. Sporulation can be divided into several stages. Stage 0: Normal conditions of a vegetative cell Stage I: Axial filament formation stage In this stage bacterial chromosome become thread like known as axial filament. Axial filaments attached to cytoplasmic membrane by mesosome . Elongation of cell take places. Stage II: forespore formation Asymmetric cell division occurs. Cell membrane forms septum near one end which encloses a small portion of DNA forming forespore.

10. Sporulation or sporogenesis 15 June 2022 Stage III: engulfment of forespore. Mother cell membrane grow around the forespore engulfing it. Forespore now has two membrane layer. Stage IV: synthesis of exosporium. Chromosome of mother cell disintegrates. Forespore starts forming primodial cortex between two membranes. Dehydration of cell.

11. Sporulation or sporogenesis 15 June 2022 Stage V: synthesis of dipicolinic acid Production of SASPs and dipicolinic acid occurs. Incorporation of calcium ions with dipicolonic acid occur forming calcium dipicolinate . Further dehydration of cytoplasm. Formation of coat layer Stage VI: maturation Maturation of endospore Stage VII: release of endospore Cell lysis and release of endospore

12. Stages of sporulation 15 June 2022

13. Spore germination 15 June 2022 Endospore remains dormant for years. But under favorable conditions each endospore germinates to give one vegetative cell. Spore germination involves 3 process . Activation of endospore: The germination of bacterial spore does not occur even when the environment is favorable unless it is first activated. At first the spore coat must be damaged by heating for several minutes. Germination : The activated spore initiates germination after binding of effector molecules. Binding of effectors molecules activates autolysis that destroy peptidoglycan of cortex. After destruction of peptidoglycan, water is taken up and calcium dipicolinic acid is released. Outgrowth : After uptake of water swelling of spore occurs along with the synthesis of DNA, RNA and proteins. A small germ cell emerges out after breaking the spore coat and begins to grow into vegetative cell.

14. Spore germination 15 June 2022

15. Medical Importance of Bacterial Spores 15 June 2022 Important features of Spores Medical Implications Spores are highly resistant to heating; spores are not killed by boiling (100°C) but are killed at 121°C. Medical supplies must be heated to 121°C for at least 15 minutes to be sterilized. Spores are highly resistant to many chemicals, including most disinfectants. Only solution designated as sporicidal will kill spores. Spores can survive for many years in soil and other inanimate objects. Wound contaminated with soils can be infected with spores and cause diseases such as tetanus, gas gangrene. Spores do not exhibit measurable metabolic activity. Antibiotics are ineffective against spores. Spores formed only when nutrients are insufficient. Spores are not often found at the site of infection because nutrients are not limiting.

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