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
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
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
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
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