Lecture #8: Cell Coverings, Endospores, Chemotaxis Flashcards
Bacterial Cell Wall
is an Interconnected Sac
Prevents cells from lysing.
Lysozyme
breaks Beta Bonds.
Lysozyme is in your tears, saliva. It is in high concentration in phagocytic cells which take in and destroy foreign material. Immune System.
Membranes are a Bi-Layer
Phospholipid (fat) sandwich. Hydrophilic heads and hydrophobic tails. Hydrophobic middle is a barrier to water and dissolved materials).
In Animals, Cholesterol is Integral
Eucaryotic membranes have steroids, and cholesterol is a common steroid in animal cells. Bacterial membranes lack steroids.
May have simpler molecule that comes from same precursor; hopanoids. Steroid-like.
Both cases, provide integrity. Important in stability, flexibility. Vary in extreme environments.
Fluid Mosaic Model
Dynamic. Proteins float in a lipid sea. May be embedded in membrane, span it, or be peripheral and associated with it.
MOVE. Don’t flip but migrate or move in specific ways.
Some are channels, pores or transporters. Some are chaperones, ATPases, carriers, receptors. Some are for identification. Some are for stability or anchoring structures (pili, fimbriae, flagella). Some are toxins (hosts, competitors).
Porins
Protein(s). Filters for hydrophilic molecules (dissolve in water). Most abundant protein structures in the o.m.
Also serve as binding sites for phages, bacteriocins.
Different types in different forms, useful in identification.
Endospores are not a Means of Reproduction
They form singly, one per cell, and germinate to produce a single cell. Spores, as a means of asexual reproduction, form in multiples in a sporangium and are a means of spreading the organism in the environment.
Endospores are a means of overweathering poor conditions. Persistence in the environment.
Endospores
Form when conditions get bad. Think about this when you are using an endospore stain to I.D. a microbe.
Extremely resilient. Spores10,000 years old and MORE have been known to germinate.
Tolerant to heat, dessication, UV radiation, disinfectants and other chemicals. What makes them so resilient???
Source of food poisoning. ‘Food poisoning by endospore.’
Endospore Resistant
Cell contents dehydrated and stabilized (in spore core). DNA bound by proteins and Ca+. Calcium Dipocolinate complexes DNA and proteins—renders them inactive, and prevents damage.
Enzymes are not active.
Upon germination, repair systems are in place.
Cortex shields the materials in the core from UV light, insulates it.
Food Poisoning
Is an intoxication*. Caused by a chemical or toxin that is ingested with food.
Foodborne pathogens can be the source of toxin (intoxication*) or can cause an infection. Different. Toxin is present upon ingestion and has its effects relatively quickly while an infection occurs after an organism has time to multiply.
Home Canning
Soil microbes (endospore formers) on vegetables are killed when canned products are cooked sufficiently. Understerilization leads to problems. Clostridium grows well under anaerobic conditions (sealed jar, crimped can) and, if not killed during the processing, multiplies in the food. Produces toxin in the endospores. Heat resistant.
Botulism
Clostridium botulinum
Insufficiently processed canned food. Home canning typical source, also some outbreaks due to products canned commercially. Mushroom example.
Bacillus cereus
grows on rice. High heat kills cells but endospores may be left behind. Reheating is not sufficient and endospores contain toxin. Japanese Rice Poisoning (the Take Out Blues).
Different Mechanism Than Eucaryotic Flagellum
Bacterial flagellum is like a whip with a trailing corkscrew. Turns at the hook.
Eucaryotic flagella have a central structure with spokes that turn around that stantion.
Chemotaxis is Directed Movement
Follows a concentration gradient. Toward attractants, away from repellents.
Smell has a different function for microbes. Smelliness is desirable—repel competitors.
Tumbles are less frequent, runs become longer. Ever more directed. Movement away from a repellent.
