 Genes & Bacteria Packet #48 Chapter #18

 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

 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

 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

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

 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

 Review

Review I PlasmidsF Plasmid Fertility Plasmid R Plasmid Resistance Plasmid

Review II Bacteria Asexual Reproduction Binary FissionBuddingFragmentation Genetic Exchange TransformationTransductionConjugation