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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,


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