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• Microscopic prokaryotes

• Most numerous organisms on Earth

• Most ancient; earliest forms of life

• Bacteria are part of every environment on Earth

• Many are adapted to places where nothing else can live 2

• Rock deposits in Australia contain fossils of bacteria 3.5 byo; in relation:– 1st Eukaryotic cells (protists) 2.5 bya– Modern Humans only came about 100,000 years ago

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• So, all modern organisms evolved from bacteria

• PROKARYOTIC: single-celled; no nucleus or membrane-bound organelles

• Few morphological differences between types of bacteria

• Do not vary much in shape & size like other organisms

• Grouped into taxa based on structure, physiology, molecular composition, & reaction to specific types of stains

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Bacteria used to be grouped into a single Kingdom, called Monera

Today, we separate them into 2 kingdoms, based on difference in ribosomal RNA

• Eubacteria– Common “germs”– Simply called “bacteria”

• Archaebacteria– Ancient, extremophiles

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• Have a unique form of rRNA• Cells walls characterized by absence of

peptidoglycan– Peptidoglycan: protein-carb

compound found in cell walls

of eubacteria

• Thought to be the ancestral organisms that gave rise to other (more modern) forms of life

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• Found in extreme environments

• More common than once thought, example:

• Methanogens: broad phylogenetic group of archaebacteria

– Convert H2 & CO2 into food and methane CH4 gas

– Found anaerobic areas; oxygen is poison to many of these

– Intestinal tracts of humans & cows

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• Extreme Halophiles: salt-loving archaebacteria; live in high salt concentration environments– Great Salt Lake & Dead Sea

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Thermoacidophiles:

• live in extreme acidic environments, high temp., low pH

• Deep sea hydrothermal vents

• Hot springs, geysers

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• Divided into MANY different phyla according to evolutionary relationships

• 4 generally recognized phyla are – CYANOBACTERIA– SPIROCHETES – GRAM-POSITIVE– PROTEOBACTERIA

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Eubacteria come in three basic shapes:

• Bacilli (bacillus): rod-shaped

• Cocci (coccus): sphere-shaped

• Spirilla (spirillum): spiral-shaped

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Cell forms:

• Diplo- pairs• Strepto: chains• Staphylo: grapelike clusters

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Identify this

• Eubacteria cell walls are made of Peptidoglycan.

• Thickness of cell wall and other membranes protects bacteria against some kinds of antibiotics by preventing their entry into the cell.

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• Most species of bacteria can be grouped into 2 categories based on their response to a laboratory technique called Gram Staining

• Taxonomists divide bacteria

into various subgroups

including Gram-Positive

& Gram-Negative Bacteria

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• Technique involves staining bacteria with purple dye (Crystal violet) & iodine

• Then rinsed with alcohol• Then restained with a red dye (Safranin)• Gram-Positive Bacteria will retain the PURPLE DYE and appear

Purple. • Gram-Negative Bacteria will appear RED (pink) from the RED

DYE• Depending on cell walls, bacteria absorbs either purple/red dye

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• Gram-Positive bacteria have thicker layer of peptidoglycan in cell wall

• Gram-Positive and Negative differ insusceptibilities to antibacterial drugs, produce different toxic materials, & react differently to disinfectants.

Gram + (top), Gram – (bottom)

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Note: Gram-negative bacteria have cell wall including an outer membrane composed of a layer of lipids and sugars: “glycocalyx”

• Composed of a– Cell Wall– Cell Membrane– Cytoplasm

• Some bacteria have distinctive structures, such as flagella, capsules, and outer membranes

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• Capsule: (glycocalyx) an additional (optional) outer covering; protects against drying or harsh chemicals & host body's white blood cells, which would otherwise engulf (eat) it

• Flagella: whip-like structure used for movement

• Pili: (pilus) short, hair-like protein structures found on the surface of some species of bacteria  – Help bacteria hold on

to host cells & can be used to transfer genetic material from one bacterium to another

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• Prokaryotes have lots of ribosomes, but no organelles with membranes

• Do not have mitochondria or chloroplasts so use cell membranes to carry out cellular respiration or photosynthesis

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•Have a single chromosome: DNA in single closed loop

•May also have small loops of additional genes: plasmids

• A spore is a dormant structure that is produced by Gram-positive bacterial species that are exposed to harsh environmental conditions.

• Cell is encased in a protective covering.

• Makes them VERY hard to kill!

• When conditions improve they break open & resume producing new bacteria cells

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This bacterium has formed an ENDOSPORE

Difference between “disinfect” and “sterilize”?

• Most Prokaryotes are heterotrophs; get their energy by consuming organic matter as a source of nutrition.

• Some are autotrophs; obtain energy by making their own food.– Phototrophs: from sunlight– Chemotrophs: from minerals

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Bacterial Reproduction

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Binary fission

• Bacteria cell goal: to grow and multiply• • Many can double number every 20 minutes!

•Use binary fission to reproduce asexually, quickly

• Process: chromosome is replicated, then the cell divides

Bacteria can also combine genes

3 ways: • Conjugation --• Transformation

(uptake of naked DNA from outside the cell)

• Transduction (virus inserts new genes into cell) Conjugation

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Eubacterial Phyla:

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• Nitrogen-Fixing Bacteria• Earth's atmosphere is 80% nitrogen

but plants and animals cannot use nitrogen in gaseous state

• We require nitrogen to make nitrogen-containing compounds like proteins and nucleic acids

• Rhizobium are essential to the nitrogen cycle

25Legumes have lots of root nodules, filled with these bacteria

• Gram-Negative bacteria that perform plant-like photosynthesis & release oxygen as by-product (waste)

• Once classified as blue-green algae• Now considered eubacteria, because they

lack a membrane-bound nucleus & chloroplasts

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• “Eutrophication”: Population Bloom of bacteria = sudden increase in # of cyanobacteria due to high availability of nutrients.

• After many cyanobacteria die; decomposed by heterotrophic bacteria.

• Consume available oxygen

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• Actinomycetes: Gram-positive bacteria that form branching filaments; used to make antibiotics.

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• Used in sewage treatment

• Decomposers, breaking down the remains of organic matter in dead plant & animal waste

• Recyclers, returning nutrients back to the environment

• Food production: Bacteria help us make buttermilk, sour cream, yogurt, some cheese, sauerkraut and pickles

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http://www.innvista.com/health/microbes/bacteria/foodprod.htm

• Industrial chemical production• • Help clean up environmental

disasters caused by humans, such as chemical & oil spills

• Useful in genetic engineering (gene splicing) to produce medicines and drugs.

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• Spoil food • Cause odor

• Some cause illness/disease, death

• "Toxins" substances released by bacteria the make you ill

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• Pathology: scientific study of disease• Pathogens: bacteria that cause disease

• Some bacteria cause disease by producing toxins (poisons)

• Exotoxins: bacterial proteins; produced by Gram-positive Bacteria – Secreted into the surrounding environment– Tetanus is a disease caused by an

Exotoxin. Ever cut yourself or step on a nail and had to take a shot?  That was to prevent Tetanus

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• Endotoxins: made of lipids & carbohydrates

• associated with the outer membrane of Gram-negative bacteria, such as E. coli– Not released until bacteria dies  – Cause fever, body aches, & weakness,

& they damage the vessels of the Circulatory System

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• Pathogenic bacteria are a major cause of human death and disease and cause infections such as tetanus, typhoid fever, diphtheria, syphilis, cholera, foodborne illness, leprosy and tuberculosis, pneumonia, Lyme disease, etc.– http://biology.clc.uc.edu/courses/bio106/bact-dis.htm

• Bacterial diseases are also important in agriculture, with bacteria causing leaf spot, fire blight and wilts in plants, as well as Johne's disease, mastitis, salmonella and anthrax in farm animals.– http://en.wikipedia.org/wiki/Bacterial_diseases

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• Many antibiotics are derived from chemicals that bacteria or fungi produce;

• 3 ways that antibiotics kill bacteria:– interferes with cell wall synthesis, ex: Penicillin– interferes with protein synthesis; ex: Tetracycline– inhibits RNA synthesis; ex: Rifampin

• They affect only the growth of bacteria without harming the body cells of humans

• Antibiotic Resistance– Overuse of antibiotics encourages drug-resistant strains

to evolve through selection– Mutant bacteria continue to grow

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