Bacteria and VirusesBacteria and Viruses

HIV Virus

Yersinia pestisGeneralized Bacterial Cell

Bacterial FactsBacterial Facts

All bacteria are prokaryotes: they All bacteria are prokaryotes: they lack membrane-bound organelles lack membrane-bound organelles within their cells.within their cells.

All bacteria are microscopic in size.All bacteria are microscopic in size. Fossils of bacteria have been found Fossils of bacteria have been found

that are 3.5 billion years old.that are 3.5 billion years old. The oldest fossils of eukaryotic cells The oldest fossils of eukaryotic cells

are 2.5 billion years old.are 2.5 billion years old.

Bacterial Evolution and Bacterial Evolution and ClassificationClassification

ArchaebacterialArchaebacterial cells have cell cells have cell walls that lack the chemical walls that lack the chemical peptidoglycan.peptidoglycan.

Archaebacterial genes have Archaebacterial genes have introns and exons, like the introns and exons, like the genes of eukaryotes.genes of eukaryotes.

Archaebacteria are more Archaebacteria are more ancient than eubacteria.ancient than eubacteria.

Today, many archaebacteria Today, many archaebacteria can only exist in extreme can only exist in extreme environments like that of the environments like that of the ancient Earth.ancient Earth.

Archaebacteria probably Archaebacteria probably evolved from an earlier evolved from an earlier ancestor that led to all of the ancestor that led to all of the eukaryotes.eukaryotes.

Most bacteria today are Most bacteria today are eubacteriaeubacteria..

Eubacterial cells have cell Eubacterial cells have cell walls that contain the walls that contain the chemical chemical peptidoglycan.peptidoglycan.

Eubacterial genes Eubacterial genes lacklack introns introns and exons, and are unlike the and exons, and are unlike the genes of eukaryotes.genes of eukaryotes.

Most eubacteria can be Most eubacteria can be grouped into two groups: grouped into two groups: Gram + or Gram -. Gram + or Gram -.

Although some eubacteria Although some eubacteria cause diseases, many more cause diseases, many more are helpful to the are helpful to the environment.environment.

Bacteria are separated into two kingdoms: Bacteria are separated into two kingdoms: ArchaebacteriaArchaebacteria and and EubacteriaEubacteria

Kingdom ArchaebacteriaKingdom Archaebacteria MethanogensMethanogens are are

archaebacteria that harvest archaebacteria that harvest energy by changing Henergy by changing H22 and CO and CO

22 into methane gas. into methane gas. They are anaerobic They are anaerobic

chemoautotrophs.chemoautotrophs. They live in the mud at the They live in the mud at the

bottom of swamps and in bottom of swamps and in sewage and in the large sewage and in the large intestines of many vertebrates intestines of many vertebrates including humans. including humans.

Extreme halophilesExtreme halophiles live in very live in very salty environments like the salty environments like the Great Salt Lake and the Dead Great Salt Lake and the Dead Sea. Sea.

They are also They are also chemoautotrophs, in that they chemoautotrophs, in that they use salt to produce ATP.use salt to produce ATP.

ThermoacidophilesThermoacidophiles are are archaebacteria that thrive in archaebacteria that thrive in very acidic environments (a very acidic environments (a pH less than 2) with very high pH less than 2) with very high temperatures (up to 110temperatures (up to 110ooC), C), such as volcanic vents on land such as volcanic vents on land or in deep water near cracks in or in deep water near cracks in the ocean floor.the ocean floor.

Thermoacidophiles can be Thermoacidophiles can be found in the hot springs in found in the hot springs in Yellowstone.Yellowstone.

Kingdom EubacteriaKingdom Eubacteria Most bacteria are Most bacteria are

eubacteria, which exist in eubacteria, which exist in many shapes and sizes. many shapes and sizes. They also have metabolic They also have metabolic and genetic differences.and genetic differences.

Eubacteria are classified Eubacteria are classified according to four basic according to four basic criteria. criteria.

I.I. Most eubacteria come in Most eubacteria come in one of three basic shapes: one of three basic shapes: rod-shape (bacillus), round rod-shape (bacillus), round (coccus), or spiral (spirilla).(coccus), or spiral (spirilla).

Bacteria Types: Bacillus

II. Bacteria are also classified by how they group together: two together (diplo-), chains of bacteria (strepto-), or clusters (staphlo-)

III.III. Bacteria can be classified Bacteria can be classified according to according to the composition of the composition of their cell walls as their cell walls as Gram + or Gram + or Gram -.Gram -.

IV.IV. Bacteria can be classified Bacteria can be classified according to according to their type of their type of respiration: obligate respiration: obligate aerobes aerobes need O2, obligate need O2, obligate anaerobes anaerobes are poisoned by O2, and are poisoned by O2, and facultative anaerobes can exist in facultative anaerobes can exist in

the presence or the the presence or the absence of O2.absence of O2.

Some Phyla of Eubacteria Some Phyla of Eubacteria PhylumPhylum ShapeShape How it How it

movesmovesImportanceImportance Type of metabolismType of metabolism Gram Gram

stainstain

CyanobacteriCyanobacteriaa

Bacilli, Bacilli, coccicocci

Gliding, Gliding, some some don’t don’t movemove

Filled Earth’s Filled Earth’s atmosphere atmosphere with oxygen.with oxygen.

Aerobic, Aerobic, photosynthetic photosynthetic autotrophsautotrophs

Gram -Gram -

SpirochetesSpirochetes SpiralSpiralss

CorkscreCorkscrew motionw motion

One type of One type of spirochete spirochete causes syphilis.causes syphilis.

Aerobic and Aerobic and anaerobic anaerobic heterotrophsheterotrophs

Gram -Gram -

Gram + Gram + bacteriabacteria

Bacilli, Bacilli, coccicocci

Flagella, Flagella, some some don’t don’t movemove

Many cause Many cause diseases like diseases like tooth decay, tooth decay, but some are but some are used to culture used to culture yogurt and yogurt and cheese.cheese.

Aerobic and Aerobic and anaerobic anaerobic heterotrophs and heterotrophs and photosynthetic photosynthetic autotrophsautotrophs

Gram +Gram +

ProteobacterProteobacteriaia

Bacilli, Bacilli, cocci, cocci, spiralsspirals

Flagella, Flagella, some some don’t don’t movemove

Enteric bacteria Enteric bacteria live in intestinal live in intestinal tracts, nitrogen-tracts, nitrogen-fixing bacteria, fixing bacteria, chemoautotropchemoautotrophshs

Aerobic and Aerobic and anaerobic anaerobic heterotrophs, heterotrophs, unusual unusual metabolism, some metabolism, some are photosynthetic are photosynthetic autotrophsautotrophs

Gram -Gram -

Photosynthetic BacteriaPhotosynthetic Bacteria Most of the world’s Most of the world’s

photosynthesis is photosynthesis is carried out by bacteria.carried out by bacteria.

There are four kinds of There are four kinds of photosynthetic bacteria, photosynthetic bacteria, classified according to classified according to the photosynthetic the photosynthetic pigment they contain.pigment they contain.

Green-sulfur bacteria Green-sulfur bacteria and purple-sulfur and purple-sulfur bacteria are anaerobic. bacteria are anaerobic. They use sulfur They use sulfur containing compounds containing compounds like Hlike H22S as an electron S as an electron source instead of Hsource instead of H22O. O. They produce elemental They produce elemental sulfur instead of Osulfur instead of O22. .

Purple non-sulfur bacteria Purple non-sulfur bacteria use organic compounds use organic compounds like acids for like acids for photosynthesis. photosynthesis.

One group of One group of photosynthetic bacteria is photosynthetic bacteria is especially important. The especially important. The cyanobacteria are cyanobacteria are responsible for the responsible for the present amounts of Opresent amounts of O22 in in the atmosphere.the atmosphere.

Several types of Cyanobacteria

Chemoautotrophic BacteriaChemoautotrophic Bacteria Chemoautotrophs do not get Chemoautotrophs do not get

their energy from the sun. their energy from the sun. Instead, they get energy by Instead, they get energy by

removing high-energy removing high-energy electrons from inorganic electrons from inorganic molecules like ammonia molecules like ammonia (NH(NH33), methane (CH), methane (CH44), or ), or hydrogen sulfide (Hhydrogen sulfide (H22S). S).

Chemoautotrophic bacteria Chemoautotrophic bacteria like like Nitrobacter Nitrobacter or or NitrosomonasNitrosomonas live in the soil live in the soil and are important to the and are important to the environment and to environment and to agriculture. agriculture.

These bacteria are important These bacteria are important in the process of nitrification, in the process of nitrification, making atmospheric Nmaking atmospheric N22 into into nitrates, which plants need nitrates, which plants need for growth. for growth.

Nitrogen is needed by all Nitrogen is needed by all living things because it is a living things because it is a component of amino acids, component of amino acids, which are the building blocks which are the building blocks of protein. Without these of protein. Without these nitrifying bacteria, plants and nitrifying bacteria, plants and other living things could not other living things could not take nitrogen into their take nitrogen into their bodies, and thus could not bodies, and thus could not survive. survive.

Nitrobacter, shown as red or orange amid other bacteria.

Heterotrophic BacteriaHeterotrophic Bacteria Most bacteria are heterotrophic. Most bacteria are heterotrophic.

They get their organic They get their organic molecules from other living molecules from other living things. things.

Along with fungi, heterotrophic Along with fungi, heterotrophic bacteria are the main bacteria are the main decomposers in the living world. decomposers in the living world.

Heterotrophic bacteria are Heterotrophic bacteria are crucial to the recycling of crucial to the recycling of molecules in the living world. molecules in the living world. They break down the bodies of They break down the bodies of dead organisms into small dead organisms into small molecules that can be absorbed molecules that can be absorbed and used by other living things. and used by other living things.

Other activities of heterotrophic Other activities of heterotrophic bacteria can be helpful or bacteria can be helpful or harmful to other living things.harmful to other living things.

More than half of our antibiotics More than half of our antibiotics are produced by various species are produced by various species of the heterotrophic bacterial of the heterotrophic bacterial genus genus StreptomycesStreptomyces. .

Another genus of heterotrophic Another genus of heterotrophic bacteria, bacteria, Staphlococcus,Staphlococcus, secretes a toxic substance into secretes a toxic substance into food that causes nausea, food that causes nausea, vomiting, and diarrhea. vomiting, and diarrhea.

Species of the bacteria Species of the bacteria RhizobiumRhizobium live symbiotically in live symbiotically in nodules on the roots of a type of nodules on the roots of a type of plants called legumes. plants called legumes.

These plants include beans and These plants include beans and peas peanuts, alfalfa, and clover, peas peanuts, alfalfa, and clover, among others. among others.

The plant nodules make an The plant nodules make an anaerobic environment for the anaerobic environment for the RhizobiumRhizobium and the bacterium and the bacterium fixes nitrogen for use by the fixes nitrogen for use by the plant. When these crops are plant. When these crops are planted, they replenish the soil’s planted, they replenish the soil’s nitrogen used by other crops.nitrogen used by other crops.

Disease-Causing BacteriaDisease-Causing Bacteria Bacteria can also be parasitic. Bacteria can also be parasitic.

When parasitic bacteria invade When parasitic bacteria invade your body, they can secrete toxic your body, they can secrete toxic substances or attack your cells. substances or attack your cells. You now have a “disease.” You now have a “disease.”

Pathogenic bacteria cause a host Pathogenic bacteria cause a host of diseases. Many of these can of diseases. Many of these can be treated with antibiotics, be treated with antibiotics, although many bacteria are although many bacteria are becoming antibiotic resistant.becoming antibiotic resistant.

Antibiotics are substances Antibiotics are substances produced by other bacteria or by produced by other bacteria or by fungi that interfere with the fungi that interfere with the growth or reproduction of growth or reproduction of disease-causing bacteria. disease-causing bacteria. Antibiotics are Antibiotics are uselessuseless against against viruses. viruses.

Many bacterial diseases have Many bacterial diseases have affected the course of human affected the course of human history. Some of these are history. Some of these are bubonic plague, cholera, and bubonic plague, cholera, and typhoid fever.typhoid fever.

Bacteria and DiseaseBacteria and DiseaseDiseaseDisease PathogenPathogen Areas AffectedAreas Affected How Spread?How Spread?

BotulismBotulism Clostridium Clostridium bolulinumbolulinum

NervesNerves Improperly preserved Improperly preserved foodsfoods

CholeraCholera Vibrio choleraeVibrio cholerae IntestinesIntestines Contaminated waterContaminated water

Dental cariesDental caries Streptococcus mutans, Streptococcus mutans, S. sanguis, and S. S. sanguis, and S. salivariussalivarius

TeethTeeth Bacteria enter the Bacteria enter the mouth from the mouth from the environmentenvironment

GonorrheaGonorrhea Neisseria gonorrhaeaeNeisseria gonorrhaeae Urethra, fallopian tubes, Urethra, fallopian tubes, epididymisepididymis

Person-to-person by Person-to-person by sexual contactsexual contact

Lyme diseaseLyme disease Borrelia burgdorferiBorrelia burgdorferi Skin, joints, heartSkin, joints, heart Tick biteTick bite

Rocky Mt. Rocky Mt. Spotted FeverSpotted Fever

Rickettsia ricketsiiRickettsia ricketsii Blood, skinBlood, skin Tick biteTick bite

Salmonella food Salmonella food poisoningpoisoning

SalmonellaSalmonella IntestineIntestine Contaminated water Contaminated water and foodand food

Strep throatStrep throat Streptococcus Streptococcus pyogenespyogenes

Upper respiratory tract, Upper respiratory tract, blood, skinblood, skin

Person-to-person by Person-to-person by sneezes, coughs, or sneezes, coughs, or direct contactdirect contact

TetanusTetanus Clostridium tetaniClostridium tetani Nerves at synapses Nerves at synapses (junctions between (junctions between nervesnerves

Contaminated woundsContaminated wounds

TuberculosisTuberculosis Mycobacterium Mycobacterium tuberculosistuberculosis

Lungs, bones, other Lungs, bones, other internal organsinternal organs

Person-to-person by Person-to-person by coughscoughs

Chart from Modern Biology, Holt, Rinehart, Winston

Comparing Bacterial Cells to Comparing Bacterial Cells to Eukaryotic CellsEukaryotic CellsBacterial CellBacterial Cell Eukaryotic CellEukaryotic Cell

Internal Internal CompartmeCompartmentsnts

They lack membrane-They lack membrane-bound organelles or bound organelles or membrane systems.membrane systems.

They have membrane-bound They have membrane-bound organelles or membrane organelles or membrane systems.systems.

Cell SizeCell Size Most are 1 micrometer Most are 1 micrometer in diameter (1 µm).in diameter (1 µm).

Most are at least 10 µm in Most are at least 10 µm in diameter.diameter.

MulticellulariMulticellularityty

All are unicellular.All are unicellular. Some are unicellular, but many Some are unicellular, but many are multicellular.are multicellular.

ChromosomChromosomeses

One circular piece of One circular piece of DNADNA

Linear chromosomes are made Linear chromosomes are made of DNA combined with histone of DNA combined with histone proteins.proteins.

Cell DivisionCell Division Binary fission onlyBinary fission only Nucleus divides by mitosis Nucleus divides by mitosis before cytokinesis.before cytokinesis.

FlagellaFlagella Made of one protein Made of one protein fiber that spins like a fiber that spins like a corkscrewcorkscrew

Made of groups of microtubules Made of groups of microtubules that contract to whip back and that contract to whip back and forthforth

Metabolic Metabolic DiversityDiversity

Have many metabolic Have many metabolic pathways that pathways that eukaryotes lack eukaryotes lack (anaerobic metabolism)(anaerobic metabolism)

All are aerobic.All are aerobic.

Viral StructureViral Structure All viruses have a nucleic acid, All viruses have a nucleic acid,

either DNA or RNA, surrounded either DNA or RNA, surrounded by a protein cover, called a by a protein cover, called a capsid. They do not have capsid. They do not have cytoplasm inside the capsid and cytoplasm inside the capsid and are not made of cells.are not made of cells.

Many viruses that infect animals Many viruses that infect animals also have an outer membrane also have an outer membrane called the envelope that called the envelope that surrounds the capsid. surrounds the capsid.

The envelope is made of The envelope is made of proteins, lipids, and glycoproteins proteins, lipids, and glycoproteins that help it attach to the cell that help it attach to the cell membrane of the host cell.membrane of the host cell.

Viruses differ greatly in Viruses differ greatly in their appearance. Some their appearance. Some are just one nucleic acid are just one nucleic acid molecule inside a protein molecule inside a protein capsid made of just one capsid made of just one protein. protein.

More complex viruses More complex viruses contain several pieces of contain several pieces of DNA or RNA, and the DNA or RNA, and the capsid can be made of capsid can be made of several different proteins. several different proteins.

Viruses are either helical in Viruses are either helical in shape (and look like rods) shape (and look like rods) or are polyhedral. The or are polyhedral. The usual polyhedron is an usual polyhedron is an isacohedron made of 20 isacohedron made of 20 triangular faces. triangular faces.

Bacteriophage viruses Bacteriophage viruses have a complex shape with have a complex shape with a polyhedral head attached a polyhedral head attached to a helical tail. to a helical tail.

Are Viruses Alive? What do you Are Viruses Alive? What do you think?think?

Cellular organization: All Cellular organization: All living things are made of living things are made of cells.cells.

Metabolism: All living Metabolism: All living things use energy to things use energy to grow, move, and perform grow, move, and perform other functions. other functions.

Homeostasis: All living Homeostasis: All living things control their things control their internal conditions even internal conditions even when external conditions when external conditions change.change.

Reproduction: All living Reproduction: All living things produce offspring.things produce offspring.

Heredity: All living things Heredity: All living things use DNA as their genetic use DNA as their genetic material.material.

Viruses do not perform Viruses do not perform homeostasis.homeostasis.

Viruses are not made of cells. Viruses are not made of cells. Viruses are composed of two Viruses are composed of two basic parts: a nucleic acid and a basic parts: a nucleic acid and a protein coat. Viruses can be protein coat. Viruses can be crystallized.crystallized.

Viruses do not use energy or Viruses do not use energy or perform any other functions of perform any other functions of living things unless they are inside living things unless they are inside of a living thing and antibiotics of a living thing and antibiotics are useless against them.are useless against them.

Viruses can only “reproduce” Viruses can only “reproduce” when inside of a living thing.when inside of a living thing.

Viruses do contain a nucleic acid. Viruses do contain a nucleic acid. Some of them contain DNA and Some of them contain DNA and some contain RNA. some contain RNA.

Since viruses do not have many of Since viruses do not have many of the characteristics of life, they are the characteristics of life, they are not considered to be alive.not considered to be alive.

Biologists have agreed upon several characteristics Biologists have agreed upon several characteristics of living things.of living things.

Viral ReplicationViral Replication Viruses can Viruses can onlyonly be be

replicated by infecting a cell replicated by infecting a cell and using the cell’s enzymes and using the cell’s enzymes and other molecules to build and other molecules to build new viruses. They cannot new viruses. They cannot reproduce by themselves.reproduce by themselves.

Bacteriophages are viruses Bacteriophages are viruses that infect bacteria. Their that infect bacteria. Their replication patterns are replication patterns are similar to the patterns of similar to the patterns of viruses that cause such viruses that cause such human diseases as colds, human diseases as colds, measles, and AIDS. measles, and AIDS.

Some viruses are described as Some viruses are described as virulent because they cause virulent because they cause disease.disease. These viruses attach to These viruses attach to a host cell, hijack its DNA, and a host cell, hijack its DNA, and after the host has produced new after the host has produced new viruses, it bursts. The newly viruses, it bursts. The newly released viruses are free to infect released viruses are free to infect other host cells. This cycle of other host cells. This cycle of immediate host destruction is immediate host destruction is called a called a lytic cycle.lytic cycle.

Viruses that infect host cells Viruses that infect host cells without killing them immediately without killing them immediately are in a are in a lysogenic cycle.lysogenic cycle. They They can stay inside their host cells for can stay inside their host cells for years. AIDS is caused by the HIV years. AIDS is caused by the HIV virus, which can remain in a virus, which can remain in a lysogenic cycle for up to 10 years lysogenic cycle for up to 10 years before causing disease before causing disease symptoms.symptoms.

Bacteriophage viruses

Viruses and DiseaseViruses and DiseaseDiseaseDisease SymptomsSymptoms Vaccine?Vaccine? Mode of TransmissionMode of Transmission

ChickenpoxChickenpox Blisters, painful rash, Blisters, painful rash, feverfever

YesYes Air currentsAir currents

MeaslesMeasles Blotchy rash, respiratory Blotchy rash, respiratory congestion, high fevercongestion, high fever

YesYes Air currentsAir currents

RubellaRubella Rash, swollen glandsRash, swollen glands YesYes Air currentsAir currents

MumpsMumps Painful swelling in Painful swelling in salivary glandssalivary glands

YesYes Air currentsAir currents

SmallpoxSmallpox Blisters, lesions, fever, Blisters, lesions, fever, malaise, often fatalmalaise, often fatal

YesYes Air currentsAir currents

Infectious Infectious hepatitishepatitis

Fever, chills, nausea, Fever, chills, nausea, swollen liver, jaundice, swollen liver, jaundice, painful jointspainful joints

YesYes Contaminated food or Contaminated food or waterwater

PolioPolio Headache, stiff neck, Headache, stiff neck, possible paralysispossible paralysis

YesYes Contaminated food or Contaminated food or waterwater

AIDSAIDS Immune system failure, Immune system failure, fatalfatal

nono Sexual contact, Sexual contact, contaminated blood contaminated blood products or hypodermic products or hypodermic needlesneedles

Chart from Biology: Principles and Explorations, Holt, Rinehart, and Winston