Transcript Prokaryotes- most numerous living organism group

Prokaryotesmost numerous living organism
group
Biology Exploring LifeChapter 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
Shapes2. Bacillus, bacilli- rod-shaped
– Various forms -short or long
– Single or in chains
– Examples•
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E. coli
Bacillus subtilus
Lactobacillus vaginalis
Pseudomonas aeruginosa
Shapes3. 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 2nd 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 growth1,2,4,8,16,32.
• 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 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 bacteriaN2-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
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Washing hands
Care in food prep.
Water control
Good hygiene
Vaccines
Antibiotics
– Major Health Concern- resistance of bacteriamutations and genetic variation