Microbial Physiology&

Genetics(Two Lectures)

ByProf. Dr. Zainalabideen A Abdulla,

DTM&H., MRCPI, Ph.D., FRCPath. (U.K.)

Second LectureSecond Lecture

Anabolism/Anabolic reactions -Require energy; bonds are formed

-Energy provided by simultaneous catabolic reactions

Example: • 2 Monosaccharides Disaccharide

• Similarly for Proteins & Nucleic Acids

• Organic: Photosynthesis; Chemosynthesis

Photosynthesis -Light energy Chemical energy )bond(

-Photoautotroph, e.g. Cyanobactia -Photoheterotroph, e.g. some bacteria

-Trap light energy into chemical bonds in ATP, Glucose More ATP by aerobic respiration

• -Oxygenic photosynthetic bacteria )Produce O2( • Anoxygenic PSB )no O2(, e.g. Bacteria use S or H

Cont./…. Photosynthesis

Q. Photosynthesis is the reverse of aerobic respiration; Why?

CO2+ Water Glucose + Oxygen

-If no light: • Survive Anaerobically by fermentation • OR: become Photoheterotrophic

Chemosynthesis -Chemoautotrophs: Chemotrophs use CO2

e.g., Primitive bacteria Archaea )methanogens(

4H2 + CO2 CH4 + 2H2O

-Chemoheterotrophs: Organics )other than CO2( e.g., Most bacteria, Fungi,

Protozoa, Animals, Humans

Bacterial GeneticsGenetics: The study of heredity

Genotype (genome): Complete collection of genes

Phenotype: Physical traits, attributes, characteristics; Dictated by genotype )manifestations(

e.g., Bacterial enzymes, capsule, flagella

Chromosome: A circular strand of linked genes

Genes: Direct all functions of cell, e.g. mRNA )product(

Mutation -DNA of gene altered Alter gene product & Trait

Transmissible to offspring

-Categories: 1. Beneficial, e.g. R to antibiotic

2 .Harmful )sometimes Lethal( e.g. Non-functioning enzyme

)Lethal( NOT always

3 .Silent: Most bacterial mutations

Spontaneous mutations •Random/Natural

•Some genes: More prone •Rate: Per 10,000 – 1 Trillion DNA replication rounds

( average 1 million) •Increased: Physical or Chemical agents )Mutagens(

Mutant )an organism with mutation(, e.g. Sabin live vaccine is a mutant strain- for poliomyelitis

Ames Test (1960): Mutagen may be also carcinogen )cause cancer(

Bacterial new genetic information 1 .Lysogenic conversion

2 .Transduction

3 .Transformation

4 .Conjugation

Plasmid • Extra-chromosomal DNA in the cytoplasm

• Genes )many or few( on plasmid

• New genetic information acquired

• Replicate with or without chromosomal DNA

( episome- autonomous or integrated plasmid)

Lysogenic ConversionPhages

1 .Virulent )lytic(

2 .Temperate )Not lytic; Lysogenic( • Lysogeny: DNA injected into bacteria but no lysis

• Prophage: Remaining phage DNA in bacteria • Lysogenic bacteria )Cell(: Bacteria with prophage; Phage DNA replicate with bacteria daughter cell

cont./… Lysogenic conversion Phage conversion: A lysogenic bacterium is capable of producing one or more new gene products and exhibit new properties )i.e. converted(.

Examples of m.o. with prophage become pathogenic : • C. diphtheriae: Diphtheria; tox gene

• S. pyogenes: Scarlet fever • C. botulinum: Botulism

• V. cholera: Cholera

Transduction (“to carry across”) -Involves temperate bacteriophages

-Prophage activated )stimulants( new viruses/ attached bacterial genes carried to other cells

-Two types: General and Specialized

Transformation -Uptake/absorb of DNA )“naked DNA”( = Competence

and “competent bacteria”

-Examples:

• S. pneumoniae: DNA extract of Capsulated + non-capsulated broth Capsulated m.o*.

• Streptococcus + Staphylococcus • Others: Bacillus, Haemophilus, Neisseria,

Pseudomonas • Latent virus gene )in human( + Bacteria

( indigenous microbiota )Parkinson Dis. *Oswald Avery and Colleagues: Experiment

Conjugation )see figures(

-Sex pilus )F pilus = conjugation bridge(

-Donor )F+( attaches Recipient )F-( bacteria by F pilus

-Pilus retracts Relaxase splits plasmid dsDNA

-Is not reproduction )Bacterial mating/ male & female( Examples: Enteric bacilli, Pseudomonas

-Transfer antibiotic resistance )R Factor= multiple drug resistance = “superbug”( and fertility factors )F+ and high frequency of recombination “Hfr+”(

Genetic engineering (≠ Recombinant DNA Technology)

-Human genes Plasmid )Vector = Vehicle(

Examples: E. coli, Yeast, Human macrophages and fibroblasts )manufacturing plants(:

• GH )somatotropin( • Somatostatin )Inhibitor(

• Insulin • Interferon

• Agriculture )resistant plants( • Marine bacterium to break oil down

Gene Therapy -Insertion of normal human gene into cells:

• Viral delivery )e.g. adenoviruses, retroviruses( • Bacterial )Bacto-infection, e.g., Salmonella(

• Synthetic vector )? For the future(

-Prescribe genes (drugs) to treat: • Autoimmune diseases

• Sickle cell anaemia • Immunodeficiency disorders

• Cancers • Many other conditions