genes & bacteria packet #48 chapter #18. the anatomy of bacteria
TRANSCRIPT
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Genes & BacteriaPacket #48
Chapter #18
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The Anatomy of Bacteria
Introduction
Recall that cells, and organisms, fall under two major categories Prokaryotes Eukaryotes
Based on the classification system, bacteria are prokaryotes and are found in Kingdom Archaebacteria and Eubacteria. More to come later on Kingdoms later.
A Look Inside Prokaryotes
In prokaryotes, ribosomes are present in two sizes: - 30 S (Subunits) 60 S
Contains polyamines and magnesium
Contain plasmids that have 7 – 8 genes A plasmid is a small ring of DNA that carries accessory
genes separate from those of a bacterial chromosome Plasmids may also be found in yeast; a eukaryote.
Shapes of Bacteria
Common shapes of bacterial cells Coccus
Spherical Bacillus
Rod shaped Spiral
Spirillum Rigid helix
Spirochete Flexible helix
Vibrous Comma shaped
Categories of Eubacteria—The Cell Wall
Most eubacteria have cell walls composed of peptidoglycan and can fall into two categories Gram positive bacteria Gram negative bacteria
Gram Positive vs. Gram Negative Bacteria
Gram positive bacteria Very thick wall Consisting
mostly of peptidoglycan
Gram negative bacteria Thin peptidoglycan layer
and an outer membrane resembling the plasma membrane
Some species of bacteria produce a capsule that surrounds the cell wall
Pilli & Flagella
Pilli Protein structures that extend
from the cell Help bacteria adhere to one
another or to certain other surfaces
Bacterial Flagella Produce rotary motion and
consist of Basal body Hook Filament Sex pilus 1 m
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Plasmids
Plasmids
Some of the genetic material of prokaryotes are found within plasmids. Generally, plasmids carry
genes that code for functions not essential for cell growth
Plasmids fall into two categories F plasmid
Fertility plasmid R plasmid
Resistance plasmid
F Plasmid
F plasmid Fertility factor
Allows bacteria to go through conjugation
F+ when plasmid is present
F- when plasmid is absent
R Plasmid
R Plasmid Resistance Plasmid
Carry genes that provide resistance to various antibiotics Chloramphenicol,
tetracycline and penicillin
Carry genes that provide resistance to heavy metals Arsenic and mercury
Importance of Plasmids
Plasmids are genetic material that are exchanged between individual bacteria.
Plasmids are responsible for the evolution of antibiotic resistant bacteria.
The exchange and/or the incorporation of genetic material via plasmids, is one of the foundations for genetic engineering and biotechnology. More to come in future packet
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Asexual Reproduction vs. Exchange of Genetic Material in
Prokaryotes
Introduction
There are three types of asexual reproduction mentioned in the packet. Asexual Reproduction
Binary Fission Budding Fragmentation
However, in addition to reproducing, bacteria also exchange genetic material in three processes separate from the processes for reproduction Exchange of Genetic Material
Transformation Conjugation Transduction
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Asexual Reproduction
Asexual Reproduction in Prokaryotes
Binary Fission Cell divides forming two
cells
Budding Bud forms and separates
from the mother cell
Fragmentation Walls form inside the cell Separates into several cells
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Genetic Exchange in Bacteria
Transformation
Genetic alteration of a cell resulting from the introduction, uptake and expression of foreign material (DNA) Bacterial cell takes in DNA
fragments released by another cell
Discovered by Fredrick Griffith while searching for a vaccine against bacterial pneumonia
Transduction
Process by which bacterial DNA is moved from one bacterium to another by a virus (bacteriophage) Covered previously
Lytic & lysogenic cycles
Conjugation
Two cells of two different mating types exchange genetic material through cell to cell contact. Mating types are determined by
the plasmids. (F+/F-)
Incorrectly regarded as the bacterial equivalent of sexual reproduction or mating
Does not involve the fusing of gametes and the creation of a zygote
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Review
Review I
Review II