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Bacteria
Characteristics
• prokaryotic• unicellular• usually have locomotion• reproduce sexually & asexually
Classification
Kingdom Archaebacteria – “ancient bacteria”-able to live in extreme environments (thick mud, hot springs, salty environments)
Kingdom Eubacteria – “true bacteria” -many are pathogenic (disease causing) -ex: E. coli
BACTERIA are classified according to:
1. Shapes of Bacteria
BASIC SHAPES:coccus-round, bacillus-rod,
spirillum-spiralPREFIXES: diplo-pairs, tetra-fours, staphylo-clusters, strepto-chains
Identifying Prokaryotes
2. Structure of Cell WallsTwo different types of cell walls are found in
eubacteria. A method called gram staining tells them apart.
Gram-positive bacteria have thinner cell walls with large amounts of peptidoglycan.
Gram-negative bacteria have thick cell walls inside an outer lipid layer.
Nutrition
• autotrophic-photosynthesis – uses light-chemosynthesis - uses chemicals
• heterotrophic
3. Metabolic DiversityProkaryotes are divided into two main
groups:–Heterotrophs get their energy by
consuming organic molecules made by other organisms.
–Autotrophs make their own food from inorganic molecules.ex. Photoautotrophs and chemoautotrophs
Metabolic Diversity
Three Types of Metabolism:a. Obligate aerobes-require a constant supply of oxygen. b. Obligate Anaerobes-Bacteria that live without oxygen because they may be killed by it. c. Facultative Anaerobes-Bacteria that can survive with or without oxygen.
Copyright Pearson Prentice Hall
4. Reproduction
a. Binary Fission Binary fission is a type of asexual reproduction in which an
organism replicates its DNA and divides in half, producing two identical daughter cells.
Copyright Pearson Prentice Hall
Growth and Reproduction
b. Conjugation During conjugation, a hollow bridge forms
between two bacterial cells, and genes move from one cell to the other.
Growth and Reproduction
c. Spore Formation In unfavorable growth conditions, many bacteria form
spores. An endospore forms when a bacterium produces a
thick internal wall that encloses its DNA and some of its cytoplasm.
binary fission
conjugation
Bacillus anthracis with endospore
ImportanceBeneficial:• decomposers• produce antibiotics• break down sewer waste• used in research• used in food making• form symbiotic relationships with humans (E. coli in intestine)• nitrogen fixation
Importance
Harmful:• cause disease in humans• cause disease in livestock• cause disease in crops