Microbiology II 13th October 2016 Anaerobic Spore Forming Gram Positive Rods Kingdom: Bacteria Family: Clostridiaceae Genus: Clostridium Main characteristics: - Gram-positive rods - Motile - have flagella (peritrichous) - 1um x 20um - Ubiquitous saprophytes - have spores so they can survive anything; they are everywhere - Love the mammalian intestine - Low G/C content - bacteria usually have a high G/C content - Produce endospores (spore-forming bacteria) - Strictly anaerobic metabolism (anaerobic respiration and fermentation; reduce sulphate to sulphite to obtain energy) - will die if exposed to oxygen. They don't use oxygen as final electron acceptor, they use sulphate instead Clostridia are Obligate Anaerobes (Anaerobic Respiration and Fermentation) Anaerobic Respiration: the electron acceptor, sulphate, is exogenous (outside the cell). Oxygen isn't used. Organic Energy and Electron Source NAD+ NADH + H+ Plasma Membrane e e Electron Transport Chain (ETC) e Aerobic Respiration Terminal exogenous Get ATP from 02 anaerobic respiration and fermentation of so,2- glucose. electron acceptor Anaerobic Respiration PMF generated to produce ATP Chemical, Transport, Mechanical work Reduces sulphate to sulphite. Less ATP is produced in Bacterial growth and anaerobic function respiration; Clostridia grows slower compared to aerobic bacteria.
Microbiology II 13th October 2016 Fermentation: the electron acceptor is an endogenous (inside cell) organic molecule e.g. pyruvate, not oxygen. Eg. lactate, ethanol, propionic acid, acetic acid etc ADP ATP Organic Energy and Electron Source NAD+ >NADH + H+ Pyruvate acts as electron acceptor. Fermentation Products SLP Oxidation of glucose provides enough energy to produce ATP from ADP. Clostridia utilise the butyric fermentation pathway and produce butyric acid from pyruvate e Endogenous electron acceptor eg. pyruvate SLP=substrate level phosphorylation Anaerobes produce an awful smell due to the formation of sulphites and other smelling byproducts. Clostridia Produce Endospores Dormant, dehydrated, and highly resistant 'survival' structures carrying bacterial DNA - allows it to survive for years e.g. 20 years until the spore can germinate again. Produced in unfavourable conditions - allows survival of bacterial DNA. If expose Clostridia to oxygen, it will form an endospore. EXOSPORIUM CORE COAT 100 mm There are terminal spores, subterminal spores, and central spores. Spores can be oval, round, or rectangular. Distinct components of the spore structure: - Exosporium - used to adhere loosely to structures - Spore coat (protein) - Cortex (peptidoglycan) - Core (low water content; small acid soluble spore proteins - SASP DPA-Ca2+) saturates DNA and protects it from wet or dry heat. DPA- Ca2+ mops up any water found in the spore; dehydrates it further. CORTEX
13th October 2016 Microbiology II Spore Formation vegetative cell free endospore 1 spore coat mother cell 1 developing spore coat ASM Digital Image Collection. Merkel Germinant (or chemicals) is another bacterial spore, which is receptor based. 1. DNA condenses and aligns in the middle of the cell 2. Vegetative cell = the mother cell 3. DNA divides into two copies 4. Mother cell invaginates to form the developing forespore 5. The mother cell membrane continues to grow and engulf the developing forespore - developing spore