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.

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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.

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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