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Biology Chapter 19 Section 1 Bacteria
Transcript of Biology Chapter 19 Section 1 Bacteria
We depend on bacteria for many things, including:
foods and beverages
removal of waste and poisons from water
mining minerals from the ground
synthesis of drugs and chemicals via genetic engineering
production of vitamins in human intestines Importance of Bacteria Growth and Reproduction 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. Cell Walls
Two different types of cell walls are found in eubacteria. A method called gram staining tells them apart.
Gram-positive bacteria have thick cell walls with large amounts of peptidoglycan.
Gram-negative bacteria have thinner cell walls inside an outer lipid layer. Identifying Prokaryotes Archaebacteria
The cells walls of archaebacteria do not contain peptidoglycan.
In addition, the DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria. Classifying Prokaryotes Classifying Prokaryotes All prokaryotes were once placed in the Kingdom Monera.
Recently, biologists divided them into two different kingdoms:
Archaebacteria Bacteria that attack and digest the tissue of dead organisms are called
archaebacteria. Bacteria that must live without oxygen are called
facultative aerobes. Rod-shaped prokaryotes are called
streptococci. Bacteria are vital to the living world.
Some are producers that capture energy by photosynthesis.
Others are decomposers that break down the nutrients in dead matter.
Bacteria are also crucial players in the nitrogen cycle as they capture nitrogen from the atmosphere in nitrogen fixation. Importance of Bacteria Binary fission is a type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells. Growth and Reproduction Prokaryotes are identified by characteristics such as:
the chemical structure of their cell walls
the way they move
the way they obtain energy Identifying Prokaryotes Eubacteria include organisms that live in a variety of environments, including:
in fresh and salt water
in the human body Classifying Prokaryotes Prokaryotes that make their own food molecules from carbon dioxide and water but live where there is no light are called
chemoheterotrophs. Which characteristic distinguishes eubacteria from archaebacteria?
Eubacteria lack peptidoglycan in their cell walls.
Eubacteria contain peptidoglycan in their cell walls.
Eubacteria lack a nucleus.
Eubacteria do not possess mitochondria. Conjugation occurs when a hollow bridge forms between two bacterial cells, and genes move from one cell to the other. Growth and Reproduction Prokaryotes 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. Metabolic Diversity Spirilla Spiral and corkscrew-shaped prokaryotes are called spirilla (spirillum, singular). Identifying Prokaryotes Cocci Spherical prokaryotes are called cocci (coccus, singular). Identifying Prokaryotes Bacilli Rod-shaped prokaryotes are called bacilli (bacillus, singular). Identifying Prokaryotes Many archaebacteria live in extreme environments.
Methanogens live in oxygen-free environments, such as thick mud and animal digestive tracts.
Halophiles live in salty environments and thermophiles in hot springs where water temperatures approach the boiling point. Classifying Prokaryotes Eubacteria have a cell wall that protects the cell and determines its shape.
The cell wall of only eubacteria contain peptidoglycan. Classifying Prokaryotes Escherichia coli (E. coli) is a typical Eubacterium Classifying Prokaryotes The smallest and most common organisms are prokaryotes
unicellular organisms that lack a nucleus. Bacteria What is gained by
exchanging DNA? Not for children under 1 year old. Can you think of other uses?