CHAPTER 23Bacteria

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SECTION 1 VOCABULARY PRETEST Prokaryote Peptidoglycan Methanogen Halophile Thermoacidophile Bacillus Coccus Spirillum Streptococcus Staphylococcus Gram-negative

bacteria Gram-positive

bacteria

A. Rod-shaped bacteriaB. Spiral-shaped bacteriaC. Sphere-shaped bacteriaD. Clusters of sphere-shaped

bacteriaE. Chains of sphere-shaped

bacteriaF. “Salt-loving” archaeaG. “Heat-living” archaeaH. Anaerobic archaea I. Protein-carbohydrate found in

bacterial cell wallsJ. Appear reddish-pink when

dyedK. Appear purple when dyedL. Cells w/ no nucleus

ANSWER KEY Prokaryote L Peptidoglycan I Methanogen H Halophile F Thermoacidophile G Bacillus A Coccus C Spirillum B Streptococcus E Staphylococcus D Gram-negative bacteria J Gram-positive bacteria K

PROKARYOTES Most numerous organisms

on Earth Found almost everywhere Fossils date back 3.5 bya

(first forms of life) Single cells with no nucleus Major source of food for

many organisms Important decomposers in

the environment Divided into two domains:

Domain Archaea Domain Bacteria

Notice that Archaea are more closely related toEukarya than to Bacteria andthus share a more recentcommon ancestor.

DOMAIN ARCHAEA Archaea = archaic (ancient) Differ from other prokaryotes in the

following ways:Cell walls do not contain peptidoglycanHave introns (portions of DNA that do not

code for proteins)Live in extreme environmentsDifferent lipids in cell membranesrRNA resembles rRNA of eukaryotesGenes resemble genes of eukaryotes

ARCHAEAL GROUPS Methanogens:

Convert hydrogen gas and carbon dioxide into methane gas.

Anaerobic Live in muddy

swamps, sewers, intestines of cows and termites

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Halophiles: “Salt-loving” archaea Live in very high salt concentrations (Great Salt

Lake and the Dead Sea)

Owens Lake in CA.The lake becameextremely salty whenthe Owens riverwas diverted to supplywater to LA. PPG operated a soda ash plant (seen in thebackground)for making glass. Thecolor is due to the millions of halophiles that now live in the lake

Thermoacidophiles:Live in acid environments (pH <2) with

very high temperatures (>230 degrees F).

Ex: Hot sulfur springs of Yellowstone National Park; deep water thermal vents (black smokers)

DOMAIN BACTERIA Unlike archaea,

members of the domain bacteria: Have cell walls with

peptidoglycan Have no introns Live in a wide

variety of environments

Have lipid membranes

rRNA is unlike rRNA of eukaryotes

Genes are unlike eukaryotes genes

BASIC SHAPES Bacteria come in a few basic shapes:

Bacilli (rod-shaped): streptobacilli (chains)Cocci (sphere-shaped):streptococci

(chains): staphylococci (clusters)Spirilla (spiral-shaped)Spirochaete (corkscrew)Vibrio (comma-shaped)

GRAM STAIN A staining technique called the gram stain illustrates a

fundamental difference between two categories of bacteria: the gram positive and the gram negative bacteria. Gram negative have complex cells walls with little

peptidoglycan. They stain a reddish color. Gram positive have simpler cell walls with a lot of

peptidoglycan. They stain a purple color.

BACTERIAL GROUPS Classifying bacteria based on

evolutionary relationships has been difficult because bacteria can pick up genes from their environment through transformation.

Most scientists recognize the following groups:

PROTEOBACTERIA Proteobacteria:

Very large and diverse group Include: nitrogen-fixing bacteria that live

in nodules inside the roots of legumes (peas, beans, alfalfa, and clover). These bacteria convert atmospheric nitrogen to ammonia, which plants can use.

Also includes some disease-causing bacteria such as rickettsia bacteria (causes Rocky Mountain Spotted Fever) and helicobacter pylori (causes stomach ulcers)

Also includes enteric bacteria (symbiotic bacteria that live in intestinal tracts of humans and animals)Ex: E. coli lives in our intestines and secretes vitamin K as well as assisting in the digestive breakdown of foods.

Other strands of E.coli and Salmonella cause food poisoning.

E.coli bacteria

GRAM-POSITIVE BACTERIA Gram-positive bacteria: will

stain purple when gram stain is applied.

Examples include: Streptococcus: causes strep

throat Clostridium botulinum:

causes botulism also used in botox injections

Lactobacilli: sours milk; used in yogurt

Bacillus anthracis: causes anthrax

Actinomycetes: soil bacteria used to make many antibiotics

CYANOBACTERIA Cyanobacteria: photosynthetic

bacteriaEarth’s first oxygen-producing

organisms and are believed to be responsible for transforming Earth’s early atmosphere

Some grow in long filamentsSome form specialized cells called

heterocysts which can fix nitrogen

SPIROCHETES Spirochetes are gram-negative spiral-

shaped bacteria.Move with a corkscrew rotationCan be free living or pathogenicEx: Treponema pallidum: causes syphilis Borrelia burgdorferi: causes Lyme disease

CHLAMYDIA Chlamydia are gram-negative bacteria that

live only inside animal cells. There cell walls lack peptidoglycan Ex: Chlamydia trachomatis: causes

chlamydia (sexually transmitted disease) and trachoma eye disease, a leading cause of blindness.

Bacteria are the purple dotsinside a cell (pinkish brown)

SECTION 2 VOCABULARY PRETEST Plasmid Capsule Glycocalyx Pilus Endospore Heterotroph Autotroph Phototroph Chemotroph Obligate anaerobe Facultative anaerobe Obligate aerobe Transformation Conjugation Tranduction

A. Sticky sugars found in bacterial capsules

B. Structure formed to survive harsh environmental conditions

C. Short, hair-like projectionD. One bacteria transfers DNA to

anotherE. Bacteria takes in DNA from its

outside environmentF. Virus introduces DNA from one

bacteria to anotherG. Small, circular loop of DNAH. Outer polysaccharide coveringI. Obtain carbon from CO2

J. Obtain carbon from other organismsK. Get energy from lightL. Get energy from chemicalsM. Can live with or without oxygenN. Must have oxygenO. Must live without oxygen

ANSWER KEY Plasmid G Capsule H Glycocalyx A Pilus C Endospore B Heterotroph J Autotroph I Phototroph K Chemotroph L Obligate anaerobe O Facultative anaerobe M Obligate aerobe N Transformation E Conjugation D Tranduction F

STRUCTURE AND FUNCTION

General prokaryotic structure includes: Capsule Cell wall Cell membrane Cytoplasm Ribosomes DNA (nucleoid

region) Pili Flagella

CELL WALL Cell wall

Provides shape and protection Made of peptidoglycan and

lipopolysaccharides (only on gram negative) Many antibiotics are designed to kill bacteria by

breaking down the peptidoglycans of their cell walls. They are most effective on gram positive bacteria.

CELL MEMBRANE Also called the plasma membrane, the

cell membrane controls what gets in or out of the bacteria cell.

Consists of a lipid bilayer and proteins

Contains catalytic enzymes for respiration and photosynthesis

DNA DNA of prokaryotes

consists of a single closed loop of double-stranded DNA

Located in a central area called the nucleoid region

Most bacteria also have small rings of DNA called plasmids Self-replicate Not necessary for cell

survival Often carry genes that allow

bacteria to cause disease Often carry genes that

provide bacteria to become resistant to antibiotics

CAPSULES Many bacteria have an outer covering of

polysaccharides called a capsule Their function:

Protection from drying outProtection from phagocytic white blood

cellsFuzzy glycocalyx capsules allow bacteria to

connect to host cells and tissues (often appears as a “halo” around stained bacteria cells

PILI Pili are short, hairlike projections that

help bacteria connect to each other and to host cells and other surfaces.

Can serve as a bridge to pass genetic material

ENDOSPORES Endospores form in gram-positive

bacteria when environmental conditions become harsh.

They can resist high temps, strong chemicals, radiation, and drying out.

Cell copies its DNA and then forms a thick, protective covering around this copy. Most of the water is removed and the endospore becomes metabolically inactive. The rest of the cell will die, but the endospore, with its DNA cargo can remain viable for centuries.

It will reactivate when environmental conditions become favorable.

Can only be killed if heated to very high temperatures under pressure.

PROKARYOTIC MOVEMENT Some move by flagella Movement toward or away from a stimulus is called taxis

Chemotaxis =response to chemical stimuli such as food or toxins.

Phototaxis =response to light

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NUTRITION AND METABOLISM Two basic needs exist for prokaryotes:

Source of carbonSource of energy

Two ways to obtain the carbon source:Heterotrophs: obtain carbon from other

organismsAutotrophs: obtain carbon from CO2

Two ways to obtain the energy source:Phototrophs: obtain energy from lightChemotrophs: obtain energy from

chemicals

MAJOR BACTERIAL NUTRITIONAL MODES

These needs can be used to divide prokaryotes into four nutritional groups:

Nutritional Mode Energy and Carbon Source

Heterotroph

Photoheterotroph Uses light energy but gets its carbon from other organisms

Chemoheterotroph Obtains both energy and carbon from other organisms

Autotroph

Photoautotroph Uses light energy and gets carbon from CO2

Chemoautotroph Extracts energy from inorganic compounds and uses CO2 as a carbon source

PROKARYOTIC HABITATS Habitats occupied are based on

biochemical abilities of different types of bacteria.

Oxygen requirements:Obligate anaerobes cannot live in the

presence of oxygen. Ex: Clostridium tetani

Facultative anaerobes can live with or without oxygen. Ex: E.coli

Obligate aerobes require oxygen to live. Ex: Mycobacteriaum tuberculosis

Temperature requirements:Psychrophilic prokaryotes: “cold-loving” grow

well in 32-68oF. Can survive Antarctic temps by growing under the surface of rocks.

Mesophilic prokaryotes: grow well in moderate temperatures between 68-104oF.

Thermophilic prokaryotes: grow well in very hot temperatures between 113-230oF.

pH requirements:Most bacteria thrive in pHs between 6.5

and 7.5Acidophiles are bacteria that thrive in low

pHs (below 6)

REPRODUCTION Usually reproduce

by binary fissionAsexual

reproductionDNA duplicatesDNA molecules

move to polesCell dividesTwo identical

daughter cells are formed

RECOMBINATION Recombination occurs when prokaryotes

exchange pieces of DNA without reproduction.

Three ways recombination can occur:Transformation —a prokaryote takes DNA

from its outside environment.Conjugation —two prokaryotes bind together

and one cell transfers DNA to the other through a sex pilus.

Transduction —viruses transfer pieces of one prokaryotes DNA to another

Transformation often involves plasmids and restriction enzymes

Conjugation involves something called the F factor to be present in the donor cell.

Transduction involves defective bacteriophages that carry host DNA instead of viral DNA.

SECTION 3 VOCABULARY PRETEST Pathology Exotoxin Endotoxin Antibiotic

resistance Zoonosis Bioremediati

on

A. Toxic substances made from lipids and carbs that are released after the cell dies.

B. Toxic substances secreted by bacteria into their environment

C. Evolution of pathogenic bacteria that antibiotics cannot kill

D. Study of diseasesE. A disease that can pass

from animal to humansF. Using bacteria to recycle

compounds in nature

ANSWER KEY Pathology D Exotoxin B Endotoxin A Antibiotic resistance C Zoonosis E Bioremediation F

BACTERIA AND HUMANS Roles of bacteria:

Cause diseaseFood productionNitrogen

fixationDecomposersBioremediation

BACTERIA AND HEALTH Pathology —study of diseases

Pathogens: disease causing agentsSome bacteria cause disease by

destroying body tissues. Ex: Streptococcus

Some bacteria cause disease by secreting toxins: Exotoxins —toxins secreted by bacteria into

their environment. Ex: Clostridium tetani secretes toxins that cause tetanus

Endotoxins —toxins released after the bacteria cell dies. They can cause fever, body aches, diarrhea, hemorrhage and weakness. Ex: E. coli

ANTIBIOTICS Antibiotics are substances used to kill

bacteria. Made naturally by some fungi and

bacteria Kill neighboring bacteria or fungi

that compete for resourcesSome (Penicillin) interfere with the

formation of cell walls by breaking down peptidoglycans

Some (Tetracycline) interfere with protein synthesis

ANTIBIOTIC RESISTANCE Antibiotic resistance is

the evolution of populations of pathogenic bacteria that antibiotics are unable to kill.

Because of over-prescription of antibiotics, many resistant genes are now on R-plasmids which can easily pass from one bacteria to the next by transformation.

This leads to multiple resistances to many antibiotics… Superbugs!

EMERGING AND INFECTIOUS BACTERIAL DISEASES Most emerging diseases develop when

infectious agents, such as bacteria, pass from wild animals to humans Zoonosis —a disease that can pass from

animal to human Zoonotic disease are on the rise due to:

Human population growth Global travel and trade

FOOD AND HYGIENE AND BACTERIA Foodborne illnesses result from the

improper preparation, handling or storage of food.

To avoid:Wash all raw fruits and vegetablesWash hands and all utensils during food

preparationRefrigerate raw foods (eggs and

lunchmeats)Cook meat thoroughly Refrigerate leftovers promptly

METHODS OF FOOD PREPARATION Several methods can be used to prevent

food spoilage by bacteria:Foods can be dried and salted: Sausages

and hamsRefrigeration: Milk and eggs Adding large amounts of sugar: Jellies

and jamsPickling adds acids which slow bacterial

growth: Pickles and relishesCooking at high temps: Meat productsSealing and canning: canned foodsAdding preservatives: bread, juice and

fruits

BACTERIA AND INDUSTRY Used in food production:

Buttermilk, sour cream, yogurt, cheeses, sauerkraut, pickles, coffee, and soy sauce

Used in chemical production: Acetone, acetic acid, enzymes,

antibiotics and insulin Used to help break down sewage

and added to laundry detergent to dissolve stains

Used in some pesticides Used in bioremediation to

breakdown pollutants Used in recombinant DNA

technology