2.2 Bacteria

Basics: Unicellular (single celled) No nuclear membrane Small (less than 2 um) Only 1 circular chromosome

Classifying bacteria: To classify bacteria, you analyze: Cell shape Cell wall Movement Type of respiration Metabolism Reproduction

Morphology / Shapes There are three common shapes of prokaryotes: 1) spherical (singular: coccus, plural: cocci) 2) rod (s. bacillus, p. Bacilli) 3) spiral (spirillium)

Morphology continued… When these bacteria cells aggregate, they can form “groups” 1) Mono = one 2) Diplo = two 3) Strepto = in a chain 4) Staphlo = cluster Ex. Steptobacilli? Staphylococci

Cell Wall (pg 64) We classify bacteria as gram positive or gram negative when analyzing cell walls We use a combination of crystal violet and iodine to STAIN a sample of bacteria If the cell wall is THICK, it usually has a THICK peptidoglycan layer. This layer will get STAINED (purple) gram positive bacteria If the cell wall has a very thin peptidoglycan layer (pale pink) gram negative bacteria

Why does the cell wall matter? The composition of the cell wall is unique to the strain of bacteria Antibiotics target cell walls If we can identify the composition, we can create specific antibiotics to target certain strains of bacteria! Certain antibiotics prevent the cell wall from forming. As pressure builds in the cell, without the cell wall the bacteria bursts and dies.

Movement There are three main structures for movement: Flagellum – tail like structure that whips around to propel the bacteria Cilia – small hair-like projections surrounding the cell that help it to “swim” back and forth Non-motile – sticky cilia like structures that keep the bacteria from moving

Type of Respiration Aerobic – grows in the presence of oxygen Anaerobic – grows in the absence of oxygen Obligate aerobes –MUST have oxygen Obligate anaerobes Facultative anaerobes – can grow with OR without oxygen

Metabolism Autotrophs Heterotrophs Chemotrophs

Autotrophs Make their own energy source by using solar energy and converting it into chemical potential energy Ex. Cyanobacteria (blue green algae)– uses photosynthesis to make glucose

Heterotrophs Obtain energy from eating other organisms Ex. E.coli - find an example of what they eat!

Chemotrophs Make their own energy from chemicals like sulfur or hydrogen sulfide Ex. Methanogen – lives in deep sea vents

EXTREME types Halophiles – LOVES salt (i.e. lives in oceans) Thermophiles – LOVES hot (ie. Lives in hot springs) Psychrophiles – LOVES cold (i.e. lives in arctic soils)

Reproduction Binary Fission (asexual) Conjugation (sexual) Endospore Formation (dormant)

Binary Fission When bacteria copies it genetic information, then splits into two identical daughter cells Refer to pg 62 and draw the diagram

Conjugation The donor cell attaches itself to the recipient cell via a pilus The donor cell donates a copy of a plasmid (circular, small DNA) A common trait / info that is passed between bacteria through conjugation is resistance to antibiotics like penicillin or ampicillin

Conjugation

Endospores When environmental conditions threaten survival, some bacteria can form endospores They are hard-walled structures that protect and store the bacterial DNA/RNA The hard walls are resistant to temperature, dehydration, radiation and toxic chemicals! They can survive from weeks to thousands of years!

Homework: Go to wiki and watch the videos posted for bacteria – make notes Read pg 65 Pg. 66 # 2-8