Bacteria Biology 11

Prokaryotic Cells Unicellular No nucleus No membrane-bound organelles Do contain DNA

2 Kingdoms Archaebacteria “ancient bacteria” Eubacteria “true bacteria”

Archaebacteria: The Extremists Live in harsh environments

Methanogens: Produce methane Live in oxygen free environments Found in swamps, marshes, stomachs of cows Sewage disposal plants- help breakdown sewage

Halophiles: Salt-loving Live in salt pools left after a lake has evaporated pools have high levels of magnesium and potassium salts Utah’s Great Salt Lake and Middle East’s Dead Sea

3. Thermoacidophiles: Heat- and acid-loving Live around deep ocean vents Temperatures are often above 100ºC Anaerobic (without oxygen) Live in hot, acidic waters of sulfur springs

Eubacteria Live everywhere except extreme environments Heterotrophs Use organic molecules as food source Some are parasites Some are saprophytes (feed on dead organisms or organic wastes – break down and recycle nutrients)

2. Photoautotrophs Photosynthetic autotrophs - Live in places with sunlight Cyanobacteria – contain chlorophyll (pigment) that traps the sun’s energy Live in ponds, streams, and moist areas of land Composed of chains of independent cells

3. Chemoautotrophs Make organic molecules Obtain energy by breaking down compounds with sulfur and nitrogen and releasing the energy in the process called chemosynthesis Bacteria in Plants– able to convert atmospheric nitrogen into the nitrogen-containing compounds that plants need

Bacteria Structure Ribosomes- protein synthesis Chromosome- single circular DNA molecule Cell Wall- support and protection Flagella- motility

Pilli (sing. Pillus) hair like structure to aid in reproduction and attaching to one another Capsule- sticky, gelatinous, surrounds cell wall to protect against desiccation Cytoplasm- thick liquid within cytoplasmic membrane Plasmid- small circular piece of DNA

If Bacteria don’t have mitochondria, how do they get their energy? Occurs at cell membrane

Identifying Bacteria Bacteria are separated into two groups based on characteristics of cell wall Cell walls made of peptidoglycan (sugar and amino acid molecules) which helps structure and maintain shape (target for antibiotics) Technique called gram staining is used to do this

Gram Stain First, crystal violet dye is added. Then, a second dye is added. Gram + bacteria retain crystal violet dye Gram – bacteria appear red or pink after a counterstain is added (commonly safranin)

Gram-positive: one thick layer of peptidoglycan (protein and sugar) Gram-negative: one thin layer of peptidoglycan and an outer lipid and sugar layer

Identifying Bacteria Growth pattern Diplo (paired arrangement) Bacteria shape (plural) Cocci (spheres) Bacilli (rods) Spirilla (spirals) Growth pattern Diplo (paired arrangement) Staphylo (grape arrangement) Strepto (chain of cells)

Strepto-Coccus

Strepto-Bacillus

Spirillum

How do bacteria get around? Flagella vs Cilia Flagella use whip like motions to move Cilia use a beating motion to move (eukaryotes only)

Remember: Bacterial DNA Circular Free floating in the bacterial cytoplasm

A well fed bacteria is two happy bacteria ATP- when used, turns into ADP (Tri-phosphate or Di-phosphate) Bacteria have a protein called DnaA that starts the process of DNA replication (first step in fission) DnaA+ADP = nothing  ; DnaA+ATP = replication

Bacteria Reproduction 1. Asexual by binary fission DNA replicated DNA pulled to separate poles as bacterium increases in size A partition forms and separate the cells Results in genetically identical cells Can be rapid –ideal conditions every 20 minutes

Plasmids Extra circle of DNA that can replicate independently Can be transferred to another Bacterium Typically carries a beneficial trait. e.g. antibiotic resistance.

2. Conjugation Bacteria conjugate if one of them have special “F” factor (fertility factor) The F+ bacteria (donor) makes a Pilus, and transfers the F plasmid to the F- recipient. Recipient is now F+ Results in a bacteria with new genetic composition

Spore Formation Endospore: tiny structure that contains a bacterium’s DNA and a small amount of its cytoplasm Encased by tough outer covering Resists drying out, extreme temperature, harsh chemicals If environmental conditions improve, then endospore germinate To kill endospores, items must be sterilized (i.e. heated under high pressure)

Metabolism 2 Types: Aerobic and Anaerobic Aerobic Bacteria require oxygen to produce energy Anaerobic Bacteria don’t require oxygen to produce energy

When typing Bacteria- Gram’s stain is #1, then comes how they make energy Obligate Anaerobic (Can’t live with oxygen) Facultative Anaerobic (can get by either way) Obligate Aerobic (Can’t live without oxygen)

Where can they get energy from?

Importance of Bacteria Ecological Role Production of nutrients Nitrogen fixation Vitamin K, B12 Breakdown of cellulose Breakdown of detritus Prevention of pathogen colonization

Production of Nutrients Soil microbes take nitrogen from atmosphere and make nitrogen containing compounds (nitrates, nitrites, etc) Some exist in symbiotic relationships (eg. Termites, legumes, clover, alder, etc)

Some bacteria produce Vitamin K (E Some bacteria produce Vitamin K (E. coli) or B12, which are not produced anywhere else

Cellulose (plant fibers) cannot be broken down by eukaryotes Many organisms exist in symbiotic relationships with bacteria in order to break down cellulose into usable sugars.

Break down of detritus Bacteria clear landscape of dead matter Returns nutrients to the soil

Prevention of colonization Take up valuable real estate that pathogenic organisms would love to inhabit Harmless or beneficial bacteria prevent harmful ones from colonizing