Prokaryotes- most 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 – 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.

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 Reproduction in Bacteria

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 CO2.- carbon cycle Nitrogen cycle- nitrogen fixing bacteria- N2-NO3 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 bacteria- mutations and genetic variation