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Bacteria - 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 (çm) 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 (type of
white blood cell).
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