Bacteria Outline

- Oldest, structurally simplest, most abundant forms of life
- Only organism with prokaryotic cellular organization
- The only members of the kingdom Monera (4800 different kinds)
- Characteristics change depending on growth conditions
- Maintenance of life depends on them - play vital role of productivity and as decomposers
- Capable of fixing atmospheric N for use by other organisms
- Used in production and fermentation of various food and as antibiotics and is being tested for
insect control
- Prokaryotes vs. Eukaryotes
- Multi-cellularity
- All bacteria fundamentally single celled
- Sometimes cells adhere within a matrix to form filaments
- Activities of bacterial colonies less integrated and coordinated than in multicellular eukaryotes
Eukaryotes Bacteria
Cell Size 10x size of bacteria 1 micrometer (?m) diameter
Chromosomes Membrane bound nucleus w/ chromosomes w/ nucleic acid & proteins No nucleus/chromosomes w/ DNA
DNA contained in cytoplasm
Cell Division and Genetic Remcombination Mitosis involving microtubules
Sexual reproduction - meiosis/syngamy Binary fusion
Lack of sexual reproduction - no equal participation
Internal Compartementalization Respirational enzymes packed into mitochondria Corresponding enzymes bound to cell membranes
Cytoplasm - no internal compartments/organelles (except ribosomes)
No cytoskeleton
Flagella Complex 9+2 structure of microtubules (whip-like motion) Simple w/ a single fiber protein flagellin
Spins like a propellar
Autotrophic Diversity Enzymes for photosyn. Packed in membrane-bound organelles (plastids)
Only 1 type of photo. - release of O2 Enzymes bound to cell membrane
Several patterns of aerobic/anaerobic photo. w/ formation of S, O, sulfate
Chemosynthesis - process where certain bacteria obtain energy from oxidation of inorganic compounds and obtain C from CO2
- Bacterial Structure
- Lypopolysaccharide - polysaccharide chain with lipids attached
- Molecules of it deposited over layer of gram positive - forming outer membrane
- Makes gram negative bacteria resistant to many antibiotics to which gram positive bacteria are susceptible
- Capsule - gelatinous layer surrounding cell
- Bacilli - straight, rod-shaped bacteria
- Cocci - spherical bacteria
- Spirilla - spirally coiled bacteria
- Spores - single-celled bodies that grow into new bacterial individuals
- Some bacteria change into stalked structures, grow long, branched filaments or form erect structures that release spores
- Bacterial cells have simple structures
- 2 kinds of cell walls - gram negative/positive
- Cytoplasm of a bacterium contain no internal compartments/organelles & is bound by a membrane encased w/i a cell wall composed of 1/more polysaccharides
- Pili - other kinds of hairlike outgrowths that occur on some bacteria cells - shorter than flagella
- Help bacterial cells to attach to appropriate substrates
- Endoscopes - resistant to environmental stress; may germinate & form new bacterial individuals after decades/centuries
- Bacterial Variation
- 2 processes lend variability to bacterial reproduction
- Mutation
- Because of the short generation time of bacteria whose populations often double in a few min., mutation plays important role in generating genetic diversity
- Genetic Recombination
- Transfer of genes from one cell to another as portions of viruses, plasmids, other DNA fragments
*Intestinal bacterium: typhoid, dysentry, other diseases
- Bacterial Ecology and Metabolic Diversity
- Bacteria most abundant organisms in most environments
- Obligate anaerobes - organisms cannot grow in presence of O2
- Facultative anaerobes - organisms that function as anaerobes/aerobes
- Aerobes - organisms that require O2
- Autotrophic bacteria
- Heterotrophs - get energy from organic material formed by other organisms (most bacteria)
- Autotrophs - obtain energy from nonorganic sources
- Photosynthetic bacteria - contain chlorophyll but not held in plastids
*Cyanobacteria, green/purple sulfur bacteria, purple nonsulfur bacteria
- Different colors caused by photosynthetic pigments
- Chemoautotrophic bacteria - derive energy from the oxidation of inorganic molecules (N, S, Fe compounds, gaseous H)
- Heterotrophic bacteria
- Saprobes - bacteria that obtain nourishment form dead organic material
- Autotrophic bacteria, capable of making their own food, obtain energy from light or the oxidation of inorganic molecules
- Heterotrophic bacteria obtain energy from breaking down organic compounds made by other organisms
- By-products of bacterial metabolism
- Antibiotics - valuable
- Botulism - food poisoning
- Salmonella - gastrointestinal disease
- N-fixing bacteria
- N fixation - carried out by nodule-forming bacteria
- Bacteria releases fixed N (when they break down proteins)
- N cycle carried out exclusively by bacteria
- Bacteria as plant pathogens
- Most plant diseases caused by bacteria
- Most bacteria that cause plant diseases are from a group of rod-shaped bacteria called pseudomonads
* Citrus canker (Florida) - destroy citrus seedlings
- Bacteria as human pathogens
- Cholera, leprosy, tetanus, bacterial pneumonia, whooping cough, diptheria
- Many diseases dispersed in food/water
- Legionnaires's Disease
- Severe pneumonia - fatal in 15-20% of victims if untreated
- Caused by legionella - small, flagellated, rod-shaped, gram/-, bacteria w/ pointed ends
- Common in water
- Attacks monocytes