CLASSIFICATION, BACTERIA, AND VIRUSES

Biology

Classification

Taxonomy is: the science of naming and classifying organisms

Linnaeus developed a two-word naming systems called binomial nomenclature. Each species is assigned a two-part scientific

name. Written in italic, with just the first word

capitalized First word: Genus Second word: species For examples, humans are Homo sapiens

Classification

Overtime, Linnaeus’s classification/taxonomy system expanded to organize living things further. This includes: Kingdom Phlyum Class Order Family Genus Species

Classification

Classification

Cladogram- a model used by evolutionary biologists to

represent evolutionary history among species

Clade- a group of species that includes a single common ancestor and all descendants of that ancestor.

Derived character- a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants.

Classification

Classification

Classification has broaden beyond kingdoms to domains: Bacteria Archaea Eukarya

Domain Bacteria

Characteristics: Unicellular prokaryotes Peptidoglycan cell wall, cell membrane,

ribosomes No membrane-bound organelles Naked DNA, single circular chromosome Asexual reproduction= binary fission Heterotrophs, photoautotrophs,

chemoautotrophs Rods, spheres, spirals: Gram positive and gram

negative

Domain Bacteria

Domain Bacteria Examples include: Bacillus, E. Coli,

Streptococcus

Domain Archaea

Characteristics Unicellular prokaryotes Cell wall (no peptidoglycans), cell

membrane, ribosomes, no membrane-bound organelles

DNA + histone proteins, single circular chromosome

Asexual reproduction = binary fission Extremophiles: halophiles, thermophiles,

methanogens

Domain Archaea

Examples: Methancoccus, Halobacterium,

Thermoproteus

Domain Eukarya

Examples: Animals, Plants, Fungi, Protists

*We will explore each Kingdom in more detail throughout the remainder of the year

Prokaryotes

All bacteria are prokaryotes- unicellular organism that lack a nucleus. small cells (about 1-10 µm) that do not

have membrane-bound organelles Found in bacteria and archaebacteria

Prokaryotes

Bacteria Surrounded by cell wall which contains

peptidoglycan Archaebacteria

Look similar to bacteria Lack peptidoglycan in cell walls Live in harsh environments

Bacteria

Prokaryotic Cell Structures:Nucleoid region –

part of the prokaryotic cell where the DNA is found

Cell membrane – innermost covering of the cell

Cell wall – outside of cell membrane

Capsule – outside of the cell wall, protective covering

(not all bacteria have it)

Bacteria

Prokaryotic Cell Structures (continued): Flagella (sing. Flagellum) –

long, whiplike structure that moves bacteria Endospore

A thick wall that encloses DNA; resistance structure enabling bacteria to survive harsh conditions

Pili – short, hair-like projection used to stick to other surfaces

and for conjugation (exchange of genetic materials between bacteria)

Cytoplasm – jelly-like fluid that dissolves substances and holds

organelles Ribosomes –

organelles that make proteins in the cytoplasm

Bacteria

Bacterial cell walls

In bacteria, the cell wall consists of a protein/carbohydrate complex called carbohydrate called peptidoglycan. They are classified based on their cell walls: Gram positive bacteria

More peptidoglycan in cell walls Appear purple under the microscope after gram

stain Gram negative bacteria

Have less peptidoglycan in cell walls Have outer membrane Apper pink under the microscope after gram stain

Bacteria- shapes

Bacilli Rod-shaped

Cocci Spherical-shaped as either:

Staph- clusters Strep-chains

Spirilla Spiral-shaped

Bacteria-shapes

Bacteria- modes of nutrition

Heterotroph Consume other organisms: Clostridium

Photoheterotroph Consume other organisms and can use light

energy: Rhodobacter Photoautotroph

Use light energy to make carbon compounds; Cyanobacteria

Chemoautotroph Use chemicals, like ammonia and hydrogen

sulfide, to obtain energy; Nitrogen-fixing bacteria

Bacteria- Aerobic, Anaerobic, and Facultative Anaerobes Aerobic

Need oxygen to live Anaerobic

Cannot live with oxygen Facultative anaerobes

Can live with or without oxygen

Bacteria- Binary Fission

Binary fission Process by prokaryotes reproduce by cell

division. Steps:

Duplication of chromosomes and separation of copies.

Cell elongates Divides into two daughter cells

Bacteria- Binary Fission

Bacteria and Disease

Pathology- the study of disease caused by pathogens (microorganism—viruses or prokaryotes– that cause disease)

Bacteria and disease

Bacteria cause disease by destroying living cells or by releasing chemicals that upset homeostasis. Damaging host tissue Releasing toxins

Bacteria and Disease

Bacteria can be controlled via: Physical removal Disinfectants Food storage Food processing Sterilization by heat

Bacteria and Disease

Bacterial diseases can be treated via- Antibiotics

Blocks the growth and reproduction of bacteria Examples: penicillin, streptomycin, and

tetracycline

Bacteria and Disease

Prevention of a bacterial disease via: vaccine-

A preparation of weakened or killed pathogens or inactivated toxins that prompt the body to produce immunity to a specific disease upon injection.

Virus

Virus A nonliving particle made of proteins and

nucleic acids. Can reproduce only by infecting living cells. Have no cytoplasm or organelles Cannot carryout metabolism or

homeostasis Can’t grow like cells.

Virus

Viruses consist of… Capsid- protein coat surrounding a virus Some viruses have an envelop that

surrounds the capsid (Influenza) Nucleic acids (either DNA or RNA)

Virus Shapes

Helical- Tobacco Mosaic Virus (contains RNA) Polyhedral- Herpes (contains DNA) , Chicken

Pox (contains DNA), Polio (contains RNA) Spherical (enveloped)- Influenza (contains

RNA) Bacteriophage- T4 (contains DNA)

BacteriophageHelical

Spherical

Virus

Viral Infections- In order to infect a cell, a virus must be able

to recognize it. Viruses must bind the proteins on their

capsid specifically to the proteins on their specific host.

Viruses then “trick” the cell to take in its genetic material.

Viruses will then make multiple copies of themselves inside the cell, ultimately destroying the cell.

Virus

Viral Infections can take place in two ways- Lytic infection Lysogenic infection

Virus

Lytic Infection The virus infects a cell, it replicates, and

the new viruses burst or “lyse” from the cell.

Virus

Lysogenic Infection host cell is not immediately taken over The virus infects a cell, the viral DNA

integrates with host DNA where it may stay for a long period of time.

The viral DNA multiplies as the host cells multiply.

Eventually, it will become lytic, and the viruses will burst from the cell.

Viruses and Disease

Viruses cause disease by directly destroying living cells or by affecting cellular processes in ways that upset homeostasis. Diseases include: Common cold Influenza AIDS Chicken pox Hepatitis Wes Nile Virus HPV (Human papillomavirus)

Viruses and Disease Ways to fight viruses-

Hygiene- Washing hands, avoiding contact with sick individuals,

coughing or sneezing into a tissue or your sleeve Vaccinations

Exposure to inactive forms of the virus that prompt the body to produce immunity to a specific disease upon injection.

Vector control West Nile Virus is carried by mosquitoes (the vector).

Controlling the population mosquitoes could eliminate the spread of the virus.

Antiviral drug therapy Attack virual enzymes that in turn slow down or stop

the infection cycle of the virus.