Prokaryotesmost numerous living organism group Biology Exploring Life
Prokaryotesmost numerous living organism group Biology Exploring Life. Chapter 16
Basic Bacterial Cell Bacteria have a basic cell structure that includes a cell wall, plasma membrane, ribosomes, DNA that is not enclosed in a membrane, pili, and flagella for movement.
Classification- Shapes 3 main shapes 1. Coccus , cocci- circular/spherical – Arrangement of cells– Pairs, chains, clusters, tetrads – Examples- prefix names • Diplococci- 2 cells • Streptococci- chain /string cells • Staphylococci- cluster-grapelike • Sarcina- tetrad
Shapes 2. Bacillus, bacilli- rod-shaped – Various forms -short or long – Single or in chains – Examples • • E. coli Bacillus subtilus Lactobacillus vaginalis Pseudomonas aeruginosa
Shapes 3. Spirillum, spirilli- spiral shaped bacteria • Examples- spirochetes – Treponema pallidum • syphilus- STD – Borrelia burgdorferi • lyme disease
Gram Stain Examples of Cocci
Gram Stain Gallery of Bacilli
2. Bacterial Cell Wall structures • Different from plants, fungi and protists • Have peptidoglycan • Bacteria are divided into 2 main groups based on differences in their cell walls. – The amount of peptidoglycan – If they have an outer lipid membrane • Gram Stain – 1884 - Hans Christian Gram Differential stain • Gram Positive Bacteria • Gram Negative Bacteria
Gram Positive Bacteria • Cell wall consists of a thick outer wall of peptidoglycan • Stain blue/purple in the gram stain test. • Retain(keep) the initial crystal violet stain color. • Do not decolorize with alcohol. • Are more sensitive to Penicillin antibiotics.
Gram Negative Bacteria • Two parts to their cell wall – An Inner thin layer of peptidoglycan – An Outer lipid membrane. • Do not retain (keep) the initial crystal violet stain. • They are decolorized due to the outer lipid membrane • They pick up the 2 nd stain ( counterstain) safranin and stain pink/red.
Gram Positive vs Gram Negative Cell walls
4. Environment • Aerobic bacteria- need oxygen to survive. • Anaerobic bacteria- live without oxygen, strict anaerobes- cannot tolerate oxygen. • Most bacteria can live in both environments– Facultative anaerobes.
Reproduction in Bacteria • Binary fission- clones-results in two identical cells – Mutations can occur in copying of DNA • Simpler than mitosis • Rapid, continuous, ~ every 20 minutes, exponential growth 1, 2, 4, 8, 16, 32. • Refrigeration slows down rate of reproduction
Bacterial Growth Curve- 4 stages- Typical S curve. 1. lag phase- start up 2. log-logarithmic phase- rapid exponential growth 3. stationary phase- limiting factors( food, water, space, waste) – Carrying capacity =most numbers of population due to limiting factors – Death rate= birth rate. 4. Death phase. Review Pg 376 - Question # 18.
3 methods of Genetic Variation • Transformation- bacteria takes up DNA from environment • Conjugation- 2 bacterial cell join and transfer genetic material- plasmids • Transduction- when viruses (bacteriophage) infect bacteria with their genes.
Transformation and Conjugation
Transduction
Endospores • Special resting cells. – Thick protective coat – surrounding the chromosome, very resistant. • Survival in unfavorable conditions – Lack of water, nutrients, heat, cold, toxins – Can last for years. – Absorb water when favorable environment and grow again. • Example- Bacillus anthracis- anthrax
4 categories of nutrition • Plants, algae, prokaryotes • Prokaryotes only • Prokaryotes, animal and fungus like protists, all fungi, all animals
Important functions of prokaryotes 16. 3 • Chemical recycling • Decomposers- break down organic waste and dead organisms in environment. – Returns carbon to atmosphere as CO 2. carbon cycle • Nitrogen cycle- nitrogen fixing bacteria- N 2 -NO 3 and ammonium to be used by plants.
Bioremediation • Use of prokaryotes to remove pollutants from water, air, and soil. • Sewage treatment • Pseudomonas sp. - oil degradation on beaches. • Thiobacillus- lives in acidic mine environments, removes lead and mercury in mine runoff. • Making vitamins and antibiotics • Genetic engineering- making protein products.
Pathogenic Bacteria • Pathogens- disease causing microorganisms. • Body defenses- examples– Skin, normal biotic flora • Bacteria poisons- toxins – 2 types • Secreted by the bacterial cell- exotoxin – Food poisoning- Clostridium botulinum – Staphylococci • Toxin is part of cell wall-endotoxin – Drop in blood pressure-shock – Salmonella food poisoning
Defenses against disease • • • Washing hands Care in food prep. Water control Good hygiene Vaccines Antibiotics – Major Health Concern- resistance of bacteriamutations and genetic variation
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