General Flashcards
(22 cards)
when did microorganisms first evolve
3.5 billion years ago
around how many species of microorganisms are always present in the air
725
when did cyano bacteria and O2 producing photosynthesising organisms appear
2.5-3 billion years ago
when did the modern eukaryotic cells appear
1.4 billion years ago
when did humans appear on earth
400 thousand years ago
what two sequences is the tree of life based on
16S and 18S rRNA sequences
what three groups are protozoans (protista) traditionally classified into
Amoebae (have pseudopodia)
Flagellates (have flagella)
Ciliates (have cilia)
what is the biological species concept suggested by Mayr in 1963
is fundamental ecological and genetic unit. groups of interbreeding natural populations that are reproductively isolated
what is the current definition of a bacterial/archael species
a category that circumscribes a genomically coherent group of individual isolates/strains sharing a high degree of similarity in many independent features, comparatively tested under highly standardised conditions
what is an open reading frame
a portion of a DNA molecule that when translated into amino acids contains no stop codons
what is polyphasic taxonomy
take information from different areas including: phenotypic data, genotypic data and phylogenetic data
what is quorum sensing
Quorum sensing is the regulation of gene expression in response to fluctuations in cell-population density.
QS bacteria produce autoinducers. Create a beneficial phenotype (survives well in high density for example)
what are common sites of primary biofilm infection
mouth (through bleeding gums), catheter entries (such as the subvenous catheter), and implanted medical devices (such as an artificial hip joint).
what are common sites of secondary biofilm infection
brain, kidneys, intervertebral spaces, bones around implanted medical device.
what is dysbiosis
an imbalances between healthy microflora and disease microflora - can lead to ill health
what is the difference between commensalism and symbiosis
Commensalism is a symbiotic relationship in which one species benefits while the other species is not affected.
Symbiosis both benefit
what are enterotypes
a classification of living organisms based on the bacteriological composition of their gut microbiota
what are the three enterotypes
- Type 1: high levels of Bacteroides
- Type 2: few Bacteroides but Prevotella common
- Type 3: high levels of Ruminococcus
what are the mechanical anatomical barriers to infection (4)
epithelial surfaces (physical impermeable barrier, desquamation)
movement of cilia (or peristalisis)
flushing action of tears and saliva
trapping effect of mucus
what are the chemical anatomical barriers to infection (6)
- Fatty acids in sweat inhibit the growth of bacteria.
- Lysozyme and phospholipase found in tears, saliva and nasal secretions can breakdown the cell wall of bacteria and destabilize bacterial membranes.
- The low pH of sweat and gastric secretions prevents growth of bacteria.
- Defensins found in the lung and gastrointestinal tract have antimicrobial activity.
- Surfactants in the lung act as opsonins (substances that promote phagocytosis of particles by phagocytic cells).
- Low pH of the stomach (1-2pH) can break down bacterial cell walls
what are the biological anatomical barriers to infection
The normal flora of the skin and in the gastrointestinal tract can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or attachment to cell surfaces.
what is sarcoidosis
a disease characterized by the growth of tiny collections of inflammatory cells (granulomas) in any part of your body — most commonly the lungs and lymph nodes. But it can also affect the eyes, skin, heart and other organs
