bacteria and bacteriophages

how do mutations affect bacteria colonies

mutations have little to no effect since each colony contains millions of bacteria

term for when one large colony covers the plate

lawn

titer formula

(# of colonies/mL plated) x DF

what comprises a bacterial genome

a circular chromosome, chromids, and plasmids

where is the bacterial chromosome located

the nucleoid

where are essential genes carried in a bacterium

the chromosome

describe chromids

similar to chromosomes and can contain essential genes, but not all bacteria have them; chromids also use the plasmid partitioning system

describe plasmids

DNA that carries non-essential genes; use the plasmid partitioning system; plasmids can be kept separate from chromosomal DNA during replication

bacterial replication

binary fission

non-integrative plasmid replication

when the

bacteria that replicate and integrate plasmid DNA with their chromosome

episomes

f plasmid

fertility; facilitates conjugation and DNA transfer between bacteria

killer plasmid

facilitate the synthesis of toxins that can kill other bacteria

degradative plasmids

facilitate the production of enzymes for metabolism of unusual molecules; used in the bacteria that break down oil spills

virulence plasmids

supports the pathogenesis of diseases; can be cancerous or cause other health problems

resistance plasmids

facilitate resistance to antibacterial genes

what are the ways bacteria receive new genetic material

conjugation, transformation, transduction

decribe conjugation

bacteria exchanging DNA; a donor cell connects to a recipient cell through a pilus and sends a copy of its chromosome

describe the f factor cycle

donor cell sends over F plasmid to recipient cell; F plasmid is integrated into chromosome creating an HFR; if the F plasmid is cut out of the HFR chromosome and takes some chromosomal DNA with it, creating an F’ cell

what molecule is needed for transformation

calcium phosphate; allows DNA into the cell

describe transformation

DNA is obtained through non-living vehicles bringing the DNA into the cell

what happens when foreign DNA enters a bacterium during transformation

endonucleases eat through one side of the DNA strand, making a single strand; crossing over can occur between the foreign DNA and bacterial DNA to create a ‘heterozygous’ bacterium

what occurs after replication of a heterozygous bacterium

½ transformant and ½ non-transformant bacteria

describe transduction

broken into the lysogenic and lytic cycles; result of bacteriophage inserting its DNA and the phage DNA integrating itself into the chromosome

describe the lysogenic cycle

bacteriophages inject viral DNA into bacterium; phage DNA inserts itself into chromosome; cell divides and creates more bacteria with phage DNA

describe the lytic cycle

follows the lysogenic cycle; phage DNA is removed from the chromosomal DNA; new phage particles are produced and burst out of the cell (lysis)

what can the lytic cycle cause on a plate

a plaque; a zone of clearing on a lawn of bacteria

what can happen during transduction that does not necessarily involve viral DNA

newly formed phages can pick up bacterial DNA instead of phage DNA, and the phage can confer the bacterial DNA into other bacteria