Microbial Structure and Function Flashcards
Four types of microbes
Bacteria (prokaryote)
Protozoa (eukaryote)
Fungi (eukaryote)
Viruses (neither prokaryotic nor eukaryotic)
Bacterial structures (2 basic shapes, 4 others)
Two basic shapes: Rod Cocci Other shapes: Spirochetes Spirillum Diplococci Diplobacilli
Prokaryote versus eukaryote: genetic material
Chromosome: single circular; paired linear
Chromosome location: nucleoid (no membrane); nucleus (membrane present)
Nucleolus: absent; present
Extrachromosomal DNA: plasmid; mitochondria and chloroplast
Prokaryote versus eukaryote: site of cellular respiration and ribosomes
Cell membrane (don’t have organelles); mitochondria
Prokaryote versus eukaryote: ribosomes
30S & 50S /70S (structurally same but different proteins – antibiotic target** bacterial protein synthesis); 40S & 60S /80S in cytoplasm (70S in organelles)
Prokaryote versus eukaryote: locomotion and adhesion
Rotating flagella and gliding; Undulating flagella and cilia , and also amoeboid movement
Sex or attachment pili (fimbriae) – important for attachment to cells in body and for bacterial genetic exchange; absent
Rods
Bacilli
Two bacilli together – Diplobacilli
Streptobacilli
Chains of bacilli
Staphlococci
Clumps
Palisades
Side by side arrangements of bacilli/ “X” “V” or “Y” figures
Cocci group arrangements
Single, diplo, tetrad, chains, clumps, cubical
Structure: spirochete versus spirillum
Spirochete: Flexible undulating corkscrew
Spirillum: RIGID corkscrew shape
Inner workings of the bacteria
Flagella and pili
Capsul
Cytoplasmic membrane
Cell envelope*
How many chromosomes do bacteria have?
One chromosome (nucleoid), tightly packed
What is the mesosome?
Chromosomal DNA attached to the bacterial membrane invaginated into the cell at the site of bacterial division. Controversial topic.
What is plasmid DNA? How is it passed on and was is its importance to the cell?
A self-replicating unit of DNA distinct from the chromosome.
Much smaller than the bacterial chromosome but contains important genetic information
Ie plasmids are usually associated with antibiotic resistance genes
Plasmids are passed on as bacteria divide/grow, but are also sometimes mobile – can transfer from one bacteria to another (usually within same species, but not always, ie streptococcal transfers to staphylococcal)
Ribosomes and Granules
Where are ribosomes distributed in the cell?
No ER, so ribosomes are found throughout the cytoplasm, and often attached to the membrane
External features of bacteria and immunology
External membranes and structures of bacteria (such as flagelli and cell walls) are highly antigenic – our immune cells make antibodies to recognize, target and destroy them.
What are the different arrangements of flagella?
Not so important
Monotrichous (Vibrio cholerae)
Lophotrichous (Bartonella bacilliformis)
Amphitrichous (Spirillum serpens)
Peritrichous (Escherichia coli)
The flagellar motor
Made of the protein flagellin and consists of a filament and basal region. The basal region has a hook and a basal body which has a rod and rings.
Gram positive organisms have 2 rings, one in the cell wall and one in the cell membrane.
Gram negative organisms have 4 rings, 2 in the cell wall and 2 in the cell membrane.
Types of pili (fimbriae)
Shorter and finer than flagella.
Two types:
1. Adherence pili – attach bacteria to surfaces.
2. Sex pili – important in bacterial conjugation; found in some gram negative bacteria.
– Pili are generally a big part of infectiousness: the ability to attach/congregate/colonize and transferring antibiotic resistance
What is the capsule? What structures does it form?
A slimy outer coating not found in all bacteria.
Usually a complex of high molecular weight polysaccharides.
A.k.a. Slime layer or glycocalyx (generally more loosely associated – adherence properties).
Can be antiphagocytic: evading macrophages
Special Note: BIOFILMS.
Hip replacement– some bacteria like to produce a biolfilm on the artificial hip disease
Cytoplasmic membrane
Phospholipid bilayer (selectively permeable) that encloses the bacterial cytoplasm
Imbedded with proteins.
Site of nutrient transport in/out.
Site of respiration.
Peptidoglycan
Part of bacterial cell walls – another site of antibiotic action because unique to each bacteria
60-90% of gram positive cell wall, much less in gram negatives.
Determines staining properties