Ch 24 - BacteriaCh 24 - BacteriaEvolution and ClassificationBiology of BacteriaBacteria and Humans

Evolution – Page 467Evolution – Page 467Classification

◦ Few morphological differences for use of classification

◦ Traditionally grouped based on structure, physiology, molecular composition, and reaction to specific types of stains

Kingdom Archaebacteria – more ancient◦ Peptidoglycan – protein/CHO cmpd found in

cell walls of Eubacteria but lacking in Archae◦ Methanogens – harvest E by converting H2

and CO2 into methane gas (bottom of swamp/sewage) anaerobic

◦ Extreme Halophiles – salt-loving; use salt to generate ATP (Great Salt Lake & Dead Sea)

◦ Thermoacidophiles – extremely acidic environs; high temps (hot springs & volcanic vents/hydrothermal vents)

EvolutioEvolutionnKingdom Eubacteria –

“Bacteria” ◦Account for most

bacteria◦baccili, cocci (strepto- &

staphylo-), spirilla◦Gram Stain

Gram-positive = retain stain (appear purple)

Gram-negative = take up 2ndary stain (appear pink)

This is what you are looking for…

Gram Staining

Evolution Evolution (cont.)(cont.)◦Phylum Cyanobacteria – “blue-green algae”

(increase in nutrients in water = increase in bacteria = eutrophication/population bloom = decrease in amount of avail. O for fish = dead fish = sad)

◦Phylum Spirochetes – Gram-negative; some aerobic, some anaerobic; move in corkscrew-like rotation

◦Phylum Gram-Positive Bacteria – not all gram-positive; some gram-negative share similar molecular similarities (ex. Actinomycetes…grow in soil and produce many antibiotics)

◦Phylum Proteobacteria - largest, most diverse Enteric Bacteria – gram neg., heterotrophic; live in

intestinal tracts; aerobic & anaerobic (E. coli & Salmonella)

Chemoautotrophs – gram neg., extract E from minerals Nitrogen-fixing – incl. gram neg., (Rhizobium = live symbiotically

with plants) Converts N gas to a usable form that plants can use

Evolution (cont)Evolution (cont)

StructurStructuree Cell Wall – both (Archae and Eu) have (few

don’t) – Eu have peptidoglycan in their cell walls…gram neg. bacteria has an outer membrane of lipids and sugars as well making it impenetrable by some antibiotics

Cell Membrane – lipid bilayer and enzymes that catalyze rxns of cell respir; no mitochondria, so cell mem creates proton gradients to carry out cell resp.

Cytoplasm – viscous; ribosomes and DNA (DNA arranged in single, closed loop; some have plasmids, too)

Capsules and Pili – made of polysaccharides allowing it to cling to cells to keep out harsh chemicals and retain moisture; protection from WBCs; glycocalyx

Structure (cont.)Structure (cont.)

Endospores – dormant structure produced by some Gram-Pos. bacterial species that are exposed to harsh environmental conditions

◦ Thick outer covering that surrounds cell’s DNA

◦ Original cell may be destroyed in harsh conditions (high temps., harsh chemicals, radiation, drying, and other environ. Extremes), endospore will survive

◦ Not reproductive

◦ When conditions become favorable, endospore will open, allowing bacterium to begin multiplying again

Movement Structures – many use flagella, but not all

◦ Can have only one or many flagella

◦ Those that do not have flagella can move using slime, some are shaped (spiral) that allow them to twist

Nutrition and GrowthNutrition and GrowthSaprophytes – Heterotrophic; feed on dead and

decaying material

Photoautotrophs – Use sunlight as E source (cyannobacteria)

Obligate Anaerobes – cannot survive in O (Clostridium tetani)

Facultative Anaerobes – Can live with or without O

Obligate Aerobes – Need O to survive (Mycobaterium tuberculosis)

Thermophilic – Grow best between 104ºF-230ºF

Genetic Genetic RecombinationRecombination

Transformation – When bacterial cell takes in DNA from its external environment; new DNA is then substituted for a similar DNA fragment in the chromosome of the bacterial cell

Conjugation – 2 living bacteria bind together; one bacterium transfers genetic information to the other◦ Genetic donor must have a specialized plasmid and pilus (binds to

recipient, forming conjugation bridge)

◦ Plasmid replicated in donor bacterium, then copy crosses bridge and cells separate

Transduction – Virus obtains a fragment of DNA from host bact.

◦ After newly formed viruses have been released, they carry the bacterial gene to a new bacterium, where it can be expressed by the recipient bacterium

Just for a giggle…

Bacteria Bacteria and and HumansHumansBacteria and disease – bacteria that

cause disease = pathogens

◦Exotoxins and Endotoxins – Exo = toxins made of protein; produced by Gram+; secreted into surrounding enviro (tetanus) by living bacteria…Endo = toxins made of lipids and CHO; outer mem of Gram-; released by Gram- when bacteria die

Endotoxins = cause fever, body aches, weakness, and damage vessels of circulatory system

◦Antibiotics – drugs that combat bacteria by interfering with various cellular functions; many derived from chemicals that bacteria and fungi produce (see Table 24-5)

◦Antibiotic Resistance – bacteria mutate and become unaffected by antibiotic designed to eradicate it; resistant population grows from mutant bacteria (reproduction and genetic recom.)…overuse encourages resistance and makes it difficult to treat certain bacteria

Useful Useful BacteriBacteriaa

Sewage Treatment◦ Break down remains of organic matter in dead plant and animal

waste (recycling C and N)

Producing/Processing Food◦ Ferment lactose; digest protein in milk;

Industrial Chemical Production◦ Produce organic chemicals and fuels; mining for minerals;

petroleum recovery; insecticides; cleaning up environmental disasters (chemical and oil spills)

ViruseVirusessStructureViral ReplicationViruses and Human Disease

StructurStructureeAdvent of Virology

◦ Wendell Stanley = work suggested that viruses may be chemicals rather than tiny cells

◦ Virology = study of viruses

◦ Provides clues to biochemistry of living organisms (mutations, combination of genetic material from different sources, & other essential processes of genetics

◦ Used by pharmaceutical companies to develop new antiviral medications

CharacteristiCharacteristicscs of Viruses of VirusesViral structure

◦Capsid – Protein coat surrounding nucleic acid

◦Envelope – Made mostly of lipids; taken from host cell mem. during replication (allows new viruses to infect host cells during 1st stage of viral replication

◦Glycoprotein – Protein containing sugar chains used to attach to host

Viral shape

Grouping Grouping VirusesViruses

Types◦DNA – May act 1.) virus may directly produce RNA that then

makes more viral proteins OR 2.) it may join with the host cell’s DNA to direct the synthesis of new viruses

◦RNA – upon entering host, viral RNA is released into host cell’s cytoplasm where it uses hosts ribosomes to produce viral proteins

◦Retroviruses – RNA virus; contains enzyme called reverse transcriptase in addition to RNA

◦Reverse transcriptase – uses RNA as a template to make DNA

Viroids – smallest known particles that are able to replicate

Prions – abnormal forms of proteins that clump together inside a cell; clumping eventually kills cell; found on mammalian cell surfaces and in brain of hosts; been linked to diseases like scrapie, mad cow disease, and possibly Creutzfeld-Jakob disease

Viral ReplicationViral ReplicationBacteriophage – viruses that infect bacteria

◦ Replication cycles are similar to those of viruses of colds, measles, and acquired immune deficiency syndrome

◦ T phages (most commonly studied) infect E. coli

Lytic Lytic CycleCycle

Virulent – virus invades host, produces new viruses, destroys host, and releases newly formed viruses◦ Attaches tail fibers to receptor site

Lysogenic Lysogenic cyclecycleTemperate – virus that replicates through this cycle and does

not kill the host immediately

Lysogeny in bacteriophages◦ Attaches to host

◦ Injects DNA

◦ Integrates viral DNA into hosts genome (prophage)

◦ Multiplication of host cell with viral DNA

Lysogeny in HIV◦ RNA virus

◦ Infects susceptible WBC

◦ Attaches to receptor site, fuses with mem

◦ Viral RNA and reverse transcriptase are

released into cytoplasm

◦ Rev.tran. Transcribes viral RNA into DNA

◦ Viral DNA inserted into hosts genome

◦ Called “Provirus”

Viral Viral EvolutionEvolutionBelieved to have evolved from early cells due

to dependence on other cells to replicateFlu viruses (influenza) invade, most

destroyed by immune systems/few escape destruction possibly due to mutation, invade cells, produce thousands

These mutations make it difficult for immune system to recognize it immediately (eventually will) and many new viruses form

Difficult to develop vaccines that prevent these viral infections over long periods of time◦ Flu vaccine targets a different strain of influenza each year

Viruses and Human Viruses and Human DiseaseDiseaseAmong most widespread

illnesses in humansMild fevers to cancers;

include several other severe and fatal diseases

Infectious Infectious DiseasesDiseases Many use humans as hosts – common cold,

chicken pox, measles, mumps, polio, rabies, hepatitis Can affect various organs (brain, liver, heart, lungs,

and skin) Rabies…virus carried in saliva of infected animal Chicken pox…highly contagious…often recovery is

usually followed by lifelong resistance…if not all is destroyed…persist as a provirus and cause shingles

Prevention and TreatmentPrevention and TreatmentAntiviral drugs – drugs that interfere with the viral

nucleic acid synthesis

◦Types of virus vaccines Inactivated – Do not replicate in a host system

Attenuated – viruses that have been genetically altered so that they are incapable of causing disease under normal circumstances Preferred over those made from inactivated viruses because

protection is greater and lasts longer

Booster shots – additional doses of some vaccines; extend a person’s protection against some viruses 1960’s = measles, mumps, and rubella 1980’s = hepatitis B 1990’s = chickenpox, hepatitis A AIDS = scientists are still working on this vaccine, but genetic

diversity and mutability create problems

Emerging Emerging VirusesViruses

New viruses emerge in different parts of world◦ Exist in isolated habitats

(infect humans when habitats are developed)

◦ Tearing down rainforests may contribute (Democratic Republic of Congo) – Ebola virus Humans exposed to virus-

infected animals Ex. Hantavirus, Manchupo virus,

HIV, Ebola(4 known strains – one affects monkeys, other 3 are deadly to humans), Lassa fever virus

Sometimes difficult to locate host and figure out where it originated

Viruses and Viruses and CancerCancerCancer = uncontrolled reproduction of cells; invade

surrounding tissue

Scientists believe that cancers may be traced to genes within normal cells…genes become mutated (by outside agent = cigarette smoke, asbestos, sunlight, chemicals, or radiation)…stimulated to multiply uncontrollably

Lysogenic viruses may trigger cancer genes See table 25-3