Bacteria and Viruses

Chapter 22

Mountain Pointe High SchoolR. LeBlanc, M.S.

100 µm 20 µm 0.5 µm

•What does um represent?

•What do the yellow structures represent and how did they get there?

•How large are these bacillus bacterial cells?

How small is life?

Fig. 22.2, p. 355

1.5 µm

bacteriophage ruptured bacterial cell

•Can you see the bacteria?

•What are bacteriophage?

•Which are larger, virus or bacteria? How much smaller?

•Are these viruses living? Why or

why not?

Characteristics of Bacteria

Metabolic Diversity Photoautotrophic (Energy from: CO2; H2O; H2; H2S)

Chemoautotrophic(Energy from: CO2; H2; S; NH4)

Photoheterotrophs (carbon source=fatty acids; carbs)

Chemoheterotrophic (parasites or saprobes)

Sizes and Shapes (all of these are unicellular) 1 - 10 micrometers Coccus Bacillus Spirillum

What is the difference between an autotroph and heterotroph?

in-text, p. 356

coccus bacillus

spirillum

Sometimes oval & flattened

Small staffs maybe skiny or fat

One or more twist; some like a comma; flexible or stiff corkscrews

Characteristics of Bacteria

Structures Cell walls

Peptidoglycan (molecules of polysaccharide cross linked with short polypeptides)

Membrane (some membrane compartments: plasma)

Characteristics of Bacteria

Glycocalyx (mesh that encloses wall; called capsule)

DNA in cytoplasm (not membrane bound)

Flagella (movement; one or more; whip like)

Gram stain (use to ID bacteria: refer to other slide)

Fig. 22.4, p. 357

0.5 µm 1 µm

0.5 µm

•Bacilli & coccus bacteria attached to human teeth. (Are these bacteria harmful?)

•E. coli dividing; Pili-filament projections

•H. pylori with its many flagella

•Pathogenic bacteria

•Found in: water, food, esp. unpasteurized milk.

Bacterial Structure

Pili are protein filaments that help

bacteria to adhere to surfaces; aids in

conjugation (sexual reproduction)

The Proper Techniques Used in Gram Staining Bacteria

stain with purple dye

stain with iodine

wash with alcohol

counterstain with safranin

Proper Gram Staining Procedures:

1. Collect bacterial sample and carefully heat-fix cells to microscope slide.

2. Add Crystal Violet, a purple dye, to the bacterial sample turning all cells purple.

3. Then add iodine, a binding agent, that causes the purple dye to stick to the gram positive bacterial cells.

4. Use an alcohol wash to rinse off the purple dye from the gram negative cells making them neutral in color.

5. Last, counter-stain the bacterial sample with safranin, a pink dye, that will stick to the gram negative cells turning them pink.

Gram Positive: bacteria cells purple.

Gram Negative: bacteria cells pink with counter stain.

Prokaryotic Fission

•When nearly doubled in size, it divides; 10-30 minutes.

•In some cases budding takes place; daughter cell buds off parent cell

•NOTICE: Cell synthesizes protein & lipid molecules causing the plasma membrane to grow moving the 2 DNA molecules apart.

•Original DNA is a single circular chromosome thread.

Fig. 22.7, p. 358

a  Bacterium (cutaway view) before DNA replication. The bacterial chromosome is attached to the plasma membrane.

b  DNA replication starts. It proceeds in two directions away from the same site in the bacterial chromosome.

c  The new copy of DNA is attached at a membrane site near the attachment site of the parent DNA molecule.

d  New membrane grows between the two attachment sites. As it increases, it moves the two DNA molecules apart.

e  At the cell midsection, deposits of new membrane and new wall material extend down into the cytoplasm.

f  The ongoing, organized deposition of membrane and wall

material at the cell midsection divides the cell in two

IDENTICAL DAUGHTER CELLS.

a  A conjugation tube has already formed between a donor and a recipient cell. An enzyme has nicked the donor’s plasmid.

b  DNA replication starts on the nicked plasmid. The displaced DNA strand moves through the tube and enters the recipient cell.

c  In the recipient cell, replication starts on the transferred DNA.

d  The cells separate from each other; the plasmids circularize. GENETICALLY IDENTICAL DAUGHTER CELLS.

nicked plasmid conjugation tube

BACTERIAL CONJUGATION

•Conjugation: the transfer of DNA from one cell to another.

•Takes place in Salmonella; streptococcus & E. coli bacteria

Plasmid: a small self-replicating circle of extra DNA & has few genes.

http://www.hhmi.org/biointeractive/animations/conjugation/conj_frames.htm

Bacterial Classification

Numerical taxonomy Bacteria are not well represented in the fossil record. Traits of unidentified bacterial cells are compared to

known bacteria. Traits include: cell shape, motility, staining attributes,

nutritional requirements, metabolic patterns, endospores or not?

Gene sequencing and comparative biochemistry are used today in classifying. Especially using rRNA Small rRNA changes can be measured & used to relate

some groups. Newest technique to ID bacteria; nucleotide sequencing

EUBACTERIA ARCHAEBACTERIA EUKARYOTES

eu= ‘typical’ Live in harsh conditions With distinct defined organelles

•The definition of ‘species’ that fits sexually reproducing organisms dos NOT fit bacteria.

•The term ‘strain’ is used to show minor differences between bacteria that are closely related.

Archaebacteria

Methanogens (“methane-makers”)

Swamps, sewage, mud, & animal guts.

Make ATP anaerobically: CO2 to CH4

Halophiles (“salt-lovers”)

Brackish ponds, salt lakes, hydrothermal seafloor vents

Extreme Thermophiles (“heat-lovers”)

Acidic soils, hot springs, coal mines, hydrothermal vents

1st living cells; no peptidoglycan in cell walls; found in unusual places.

Methanogen with thick polysaccharide walls called peptidoglycan.

•Methano-coccus

•Heat-loving and methane producer

Cows belch producing a unique smell. Great Salt Lake; Which bacteria live there?

Commercial seawater evaporating ponds. Hypersaline condition.

Hot, sulfur-rich water in Emerald Pond, Yellowstone National Park.

Which major archaebacteria group is represented below????

Eubacteria

Photoautotrophic Cyanobacteria (blue green algae)

Ponds and freshwater (see next slide)

Chemoautotrophic Environment

Cycling of N2 , S2

Building blocks of amino acids (proteins)

Without nitrogen there would be NO LIFE.

Plants use nitrogen fixing bacteria to recycle nitrogen.

NOTE: They have fatty acids incorporated into their plasma membrane.

EubacteriaChemoheterotrophic

Most bacteria fall into this category.

Pseudomonads (decompose organic

even pesticides

Lactobacillus (‘good’ bacteria; making

pickles, yogurt, buttermilk; sauerkraut)

E. Coli (produce vitamin K/other

compounds)

Pathogenic (Disease causing; some E.

Coli; Botolinum

Endospores (Tetanus found in the soil)

resting spore heterocyst

5 µm

Cyanobacteria

•Nutrient rich pond

•Heterocyst: modified cells that form when nitrogen compounds are scarce; make a

nitrogen-fixing enzyme

developing endospore (Resting structure)

2.2 µm

•Triggered by the depletion of nitrogen or other nutrients.

•When plasma membrane breaks it releases many free spores.

•Can remain dormant for decades.

•When conditions are favorable they become active as a bacterial cell.

Facts About BacteriaAlso classified by their arrangements.

Some exist alone, most are grouped together:

Diplo - paired cells

Staphylo - clustered cells

Strepto - cells in chains

•Moves from host to host inside the gut of insect (tick) as bacteria.

•Penetrates the cytoplasm & nucleus of host cells.

•Lyme Disease: transmitted from deer ticks.

What causes this

condition?

Rocky Mountain

Spotted Fever

Different examples of bacterial infections

Match the picture with the bacterial infection: A) LEPROSY B) LYME DISEASE C) PINK EYE D) ATHELETES FEET

                                                                                          

0.25 µm

Magnetotactic Bacterium

Myxobacteria with fruiting bodies

Viruses, Viruses,

and Viruses

The Viruses Non-cellular infectious agent

Infect: cats, cattle, birds, insects, plants, fungus, protist, & bacteria (can infect organisms in ALL kingdoms).

Protein coat surrounding a nucleic acids core Rod-like or polyhedral shapes

Used for protection, shape can change, used to attach to host cells (attach to proteins in plasma membrane of host.

DNA or RNA

Reproduce inside a host cell

Enveloped or non-enveloped

Fig. 22.16, p. 364

viral RNA

protein subunits of coat

18-nm diameter, 250-nm length 80-nm diameter

lipid envelope; proteins span the envelope, line its inner surface, and spike out above it

viral RNA

reverse transcriptase

viral coat (proteins)

100-120 nm diameter

DNA

protein coat

sheath

base plate

tail fiber

65-nm diameter head, 225-nm total length

•Tobacco Mosaic Virus

•Helical Virus

Polyhedral Virus

VirusesShape

Helical (Rod Shaped)

Polyhedral

Enveloped or non-enveloped Spiked (some)

Complex Viruses are host

specific

BacteriophagesUsed to study viruses

Reproduce rapidly

Polyhedral Virus

Viruses

BacteriophageInfects bacteriaUsed in early

experiments to determine function of DNA

VirusesEnveloped virusEnvelope is made

mostly of membrane remnents from previously infected cell

HIV is example Trigger for AIDS Attacks certain

W.B.C. Weakens immune

system

Infectious Agents Tinier Than Viruses

(more stripped down than viruses) Prions (8 rare diseases of nervous system)

Small Proteins

Altered products of a gene found at the surface of neurons of nervous system.

Mad Cow Disease (BSE)*

Diseases Kuru (brain)

Scrapie (sheep); named after sheep scrape off their wool.

Creutzfeldt-Jakob disease (destroys muscle & brain function)

*Outbreak in 1996. Caused by ground up sheep with Scrapie where feed to cattle in turn spread to cattle, then to humans.

Infectious Agents Tinier Than Viruses

Viroids Tight folds or circles of RNA

Plant diseasesDestroy million of $ of:

• Potatoes

• Citrus

• Other cash crops.

Viral Multiplication Cycles

5 Steps

Attachment

Penetration

Replication

Assembly

Release

Lytic pathway Host cell lysis

Lysogenic pathway Viral DNA

integrates into bacterial chromosome

Lytic Cycle

The Lysogenic Cycle

Multiplication Cycle of a Bacteriophage Virus

In Conclusion

After the origin of life, a divergence occurred leading to Eubacteria and common ancestors of Archaebacteria and Eukaryotic cells

All bacteria are prokaryotes

Bacteria have 3 basic shapes: cocci, bacilli, and spirilla

In Conclusion

Many bacteria have external structures that increase their survival and pathogenicity

Bacteria reproduce by binary fission

Many species have plasmids and some can transfer genetic information through the process of conjugation

Bacteria as a group have metabolic diversity

In Conclusion

Viruses are nonliving infectious agents

Viruses consist of either DNA or RNA surrounded by a protein coat

Some may have an envelope and spikes

Viruses cannot reproduce on their own but must use a host cell’s machinery

There are five steps in the multiplication cycle of a virus

In Conclusion

There are two pathways common in the multiplication of bacteriophages: lytic and lysogenic

Multiplication cycles of viruses are diverse; may occur rapidly or can enter a latent phase

developed by M. Roig