Lecture 21: Micro-organisms: Classification, structure, and replication Flashcards
Characteristics of Bacteria:
Bacteria are simple, single cell organisms.
Bacterial cells lack a membrane bound nucleus.
Cells like these are prokaryotes not eukaryotes
Not all prokaryotes are bacteria!
What are the three domains?
1) bacteria
2) archaea
3) eukaryotes
What two Linnean subgroups are used when naming bacteria?
genus and species
What genetics are used in modern classification of bacteria?
hypervariable regions in 16S ribosomal RNA
Name two places where genetic information is found in bacteria:
1) nucleoid
2) plasmids
How many chromosomes do bacteria cells have?
1
Where is the bacterial chromosome located?
nucleoid
What is the function of the flagella?
Locomotion
What term is used to describe a single flagella at a single pole of the cell?
monotrichous
What term is used to describe numerous flagella at a single pole of the cell?
lophotrichous
What term is used to describe single flagella at two opposite poles of a cell?
amphitrichous
What term is used to describe multiple flagella at opposite poles of a cell?
pertirichous
What is the function of pilli/ fimbriae?
adhesion to other cells
What type of macromolecule makes up bacterial plasmids?
polysaccharide
What 3 things do bacterial plasmids protect bacteria from?
1) phagocytosis and immune responses
2) antibiotics
3) desiccation
What is desication?
Drying out
What is another term for a capsule?
slime layer
What is a biofilm?
a community of bacteria grouped by a surrounding extracellular polymeric capsule
What are endospores?
inert versions of bacteria that store genetic material in harsh conditions
Give two genuses of bacteria that can form endospores:
1) Bacillus
2) Clostridium
Describe gram positive cell walls:
thick peptidoglycan layers (up to 40 layers)
Give 4 gram positive bacterial genuses:
1) Clostridium
2) Bacillus
3) Streptococcus
4) Staphylococcus
Why is it that gram positive bacteria are likely to be found on the skin?
the thick peptidoglycan wall prevents the bacteria from drying out
Describe gram negative cell walls:
thin peptidoglycan layer with an inner and outer membrane
Why is it that many gram negative bacteria are resistant to numerous antibiotics?
Why is it that many gram negative bacteria are resistant to numerous antibiotics?
What molecules cover the outer membrane of gram negative bacteria?
lipopolysaccharide endotoxins
Describe mycobacterial cell walls:
waxy outer layer
Give an example of a bacteria genus that has no peptidoglycan in their cell wall:
Chlamydia
What colour does gram positive bacteria turn in a gram stain test?
blue/ purple
What colour does gram negative bacteria turn in a gram stain test?
Pink
What is the name given to spherical bacteria?
coccus
What is the name given to rod shaped bacteria?
Bacillus
What is the name given to long, wiggly bacteria?
Spirochele
What is the name given to long, thin and overlapping bacteria?
Filamentous
What is the name of two spherical bacteria joined together?
Diplococci
What is the name of a chain of spherical bacteria?
Streptococci
What is the name of a grape bunch of spherical bacteria?
Staphylococci
What mechanism of replication does bacteria use?
binary fission
What is horizontal gene transfer?
the movement of genetic material between cellular organisms
What are the three types of horizontal gene transfer seen in bacteria?
1) conjugation
2) transformation
3) transduction
What is conjugation horizontal gene transfer?
a pilus providing union between cells for lateral genetic transfer
What is transformation horizontal gene transfer?
a cell grabbing genetic material from the external environment and adding it to the genome via homologous recombination
What is transduction horizontal gene transfer?
where a bacteriophage adds genetic material to a bacterial cell via homologous recombination
What is a bacteriophage?
A virus that infects bacteria
Are fungi eukaryotic or prokaryotic?
Eukaryotic
What molecule is a key component in fungal cell walls?
Chitin
What are yeasts
Unicellular fungi
What are moulds?
multicellular, filamentous fungi
Is thrush caused by a yeast or mould?
Yeast
What infectious effects do moulds have?
they cause common superficial infections such as ring worm and athletes foot
True or false: moulds can reproduce sexually or asexually
True
Give two examples of helminths:
1) Schistosoma
2) Taenia
True or false: parasites can be unicellular or multicellular eukaryotes
True
True or false: parasites can reproduce sexually or asexually
True
What is a common survival mechanism used by parasites in reproductive cycles?
Cyst formation
True or false: viruses are livng organisms
false
Describe the basic structure of viruses:
nucleic acid core wrapped in a protein coat
Where do viruses get their lipid envelopes from?
host cells (helps them evade host’s immune system)
How do retroviruses add their genetic material to host cell genomes?
they convert their RNA into cDNA using reverse transcriptase
Describe the virus cycle: (5)
1) they attach to host cells using receptors and enter via endocytosis
2) they un-coat and target the nucleus with its genetic material
3) this leads to the production of early viral proteins such as integrase and polymerase
4) later, late viral proteins such as capsid molecules are produced
5) viruses are released from host cells via cell lysis or budding
What are prions?
Misfolded proteins
How do prions cause disease?
they aggregate and cause misfolding of native proteins
Give two examples of prion diseases:
1) Creutzfeldt Jakob disease
2) Kuru
