Flashcards in Introduction to microbiology Deck (55):
single cell nucleus lacking membrane bound nucleus.
all other cells with nuclei
what percentage of cells in the human body are of human origin
what type of organism do most microbiota in the human body consist of
what organism is commonly found on the hard surface of teeth
what organism is commonly found on the soft tissues of the mouth
what vitamin do the bacteria of the gut provide us with
what chemical/ element required for life is produced by bacteria of the body
what term is used to describe bacteria which cause disease
pathogenic or virulence
do all bacteria in the body cause harm
what is used to identify or determine whether an organism causes disease or not.
what is stated in koch's postulates (4 points) for an organism
The causative organism must be isolated from every individual suffering from the disease in question.
The causative organism must be cultivated artificially in pure culture.
When the causative organism is inoculated from pure culture, the typical symptoms of the infection must result.
The causative organism must be recoverable from individuals who are infected experimentally
what is stated in koch's postulates for virulent genes. (6 factors)
The gene encoding the trait of interest should be present and transcribed/translated in a virulent strain.
the gene encoding the trait of interest should NOT be present or should be silent in a strain that does not cause disease;
disruption of the gene in a virulent strain should result in the formation of a strain that is incapable of casing disease;
introduction of the gene into a strain that previously did not cause disease should transform the strain into one that does cause disease;
the gene must be expressed during infection;
antibodies raised against the gene product
or the appropriate cell-mediated immunity
should protect experimental subjects
what are the main issues with Koch's postulates
difficulty of isolation the causative agent.
impossible to grow some
what is the basic structure of a virus
nuclei acid core with a protein coat.
some may have an envelope.
are viruses intracellular or exracellular.
Viruses are obligate intracellular parasites.
how do reteroviruses cause disease.
Retroviruses are unusual in that the virion carries an RNA copy of the genome but upon infection of a host cell a cDNA copy of the virus genome is made using the enzyme reverse transcriptase and put into the human genome.
what organism causes plant infections
what organism is spongiform encephalopathies classed as
naked, infectious RNA molecules that are not associated with any proteins.
are fungi, prokaryotic, eukaryotic or akaryotic.
what is the cell wall of fungi made from
chitin- polymer of N-acetyl glucosamine
a type of fungi that grow in mats of tiny filaments known as hyphae that form mats called mycelia.
are moulds multicellular or unicellular
are yeasts multicellular or unicellular
what is the most common yeast infection
thrush" caused by Candida albicans.
what is the most common mould infection
superficial infections such as ringworm and athlete's foot.
Are protista eukaryotes, prokaryotes or akaryotes
what are the 4 classes of protista.
1. apicomplxa (formerly sporozoa),
2. flagellate protista,
3. ciliate protista and
what organism was considered a protist but is known known to be a virus
which protists organism causes vaginal infections and what is a symptom of this
are bacteria prokaryotes, eukaryotes or akorytes
explain the crystal violet test for gram -ve and gram +ve organisms,
o Apply crystal violet to bacteria and it chousl stain violet
o Add iodine
o Wash with ethanol
o If the stain is removed it is gram –ve bacteria and if the stain remains it is gram +ve bacteria.
what is the envelope of gram positive bacteria made up from
30-40 layers of a uniquely bacterial polymer “peptidoglycan
(short peptides containing both D- and L- amino acids.)
what is the envelope of gram negative bacteria made up from
very little peptidoglycan: it possesses an extra, complex “outer membrane”.
what additional membrane of gram -ve bacteria contains what
outer leaflet containing lipopolysaccharide.
sugars- form antigens on the bacterium.
lipid- acts as a endotoxin (responsible fro gram -ve shock).
what is the function of flagella on bacteria
what is the function of hair like strutures fimbrae on gram -ve bacteria.
helps adhesion onto a particular surface.
what is the function os a capsule around bacteria
helping to prevent the cell from being killed- phagocytosis
gram - ve bacteria also undertake conjugation, what is conjugation
Gram-negative bacteria exchange genetic material through sex pili tubes
what is the function of slime produced by bacteria
help them to stick to surfaces.
what is the function of endospores produced by some bacteria
resist a range of hazardous environments, and protect against heat, radiation, and desiccation.
what are the most common ways in which infection is spread
Person-to-person spread of infections- airborne.
direct inoculation.- sharing needles of blood transfusion.
faceal oral route
animals are the reservoir for bacteria such as Salmonella enteric.
Inanimate objects such as paper, pens, surgical instruments, etc. may also act as the vectors of infection
what organisms are spread via the faecal oral route
Typhoid, cholera, dysentery, hepatitis A and poliomyelitis
what mechanisms do bacteria use to cause disease
produce structures that enable micro-organisms to attach to the surface at which they cause disease.
produce toxin- endotoxin or exotoxin.
initiating undesirable consequences of the host defences.
define virulence factor
The traits used to complete the cycle of infection
pathogenic bacteria produce soluble antigens, what molecules do these bind to.
combine with antibodies to produce circulating immune complexes.
why are immune complexes in circulation a problem
trapped in blood vessels
glomerulonephritis is a immune complex mediated condition which bacteria causes this.
kidney damage following an infection with Streptococcus pyogenes.
what is rheumatic fever
immunological cross-reactions between human tissue antigens and antigens on Streptococcus progenies (or any streptococcal infection)
what is the pathogenesis of TB
Mycobacterium tuberculosis produces disease by over-stimulation of our immune response to infection.