Prokaryotes Flashcards
History of microbiology #2
History of microbiology #2
- Antony van Leeuwenhoek was first to observe and accurately describe microbial life
- Modern electron microscopes allows the study of cell substructure
- Louis Pasteur refutes idea of spontaneous generation (idea that living things arise spontaneously from other living thins)
History of microbiology #3
- Robert Koch studied anthrax; proposed four postulates to prove a casual relationship between a microorganism and a disease
- ## 1) the microorganism
Prokaryotic Diversity
- Oldest, structurally simplest, and most abundant forms of life
- Abundant for over a billion years before eukaryotes appeared
- 90-99% unknown and undescribed
- Fall into 2 domains
- Bacteria
- Archea
- Manu archea are extremophilies
Characteristics of Prokaryotes #1
- Unicellularity
- most are single-celled
- May stick together to form associations and biofilms
- Cell size
- Size varies tremendously
- Most are less than 1 um in diameter
- Nuceloid
- Chromosome is single circular double-stranded DNA
- Found in the nucleoid region of cell
- often have plasmids
- Cell division
- Most dicide by binary fission
Characteristics of prokaryotes #2
- Genetic recombination
- Exchange genetic material Extensively Through horizontal gene transfer; not a form of reproduction
- Internal Compartmentalization
- No membranse-bounded organelles
- No internal compartment
- Plasma membrane can be extensively infolded
- Flagella
- Simple in structure
- Different from eukaryotic flagella
- Metaboliv
Bacteria and archea differ fundamentally
- They differ in four key areas
Bacteria vs Archea
Earl classification characteristics
- Prokaryotes not easily classified according to forms
- Early systens relied on staining characteristics and observable phenotypes
1) Photosynthetic or nonphotosynthetic
2) Motile or nonmotile
3) Unicellular, colony-forming, or filamentous
4) formartion of spores or division by tranverse binary fission
5) Importance as human pathogens or not
molecular classification #1
1) Amino acid sequences of key proteins
2) percent guanine-cytosine content
3) Nucleic acid Hybridization
- closely related species will have more base pairing
4) gene and RNA sequencing
- Especially rRNA
5) Whole- genome sequencing
Molecular Classification #2
- Based on these molecular data, several prokaryotic groupings have been proposed
- Bergey’s Manual of systematic Bacteriology
prokaryotic cell structure
3 basic shapes
- Bacillus- Rod shaped
- Coccus- Spherical
Prokaryotic cell walls #1
1) Gram positive bacteria
- Thick, compled network of peptidoglycan
- Also contains Lipoteichoic and teichoic acid
2) Gram negative bacteria
- Thin layer of peptidoglycan
- Second outer membrane with lipopolysaccharide
- Resistanr to many antibiotics
Prokaryotic cell characteristics
1) Cell wall
- Peptidoglycan forms a rigid network
- mantains shape
- withstands hypotonic enviromenmts
- Archea have a similar molecule (pseudomurein)
2) Gram
Prokaryotic cell walls #2
1) Slayer
- rigid paracrystalline layer found in some bacteria and archea
- Outside of peptidoglycan ir outer membrane layers in gram-negative and gram-positive bacteria
- Diverse function-often involves adhesion
2) capsule
- gelatinous layer found in some bacteria
- Aids in attatchment
- Protects from the immune system
