Quiz 3 Flashcards
Characteristics that make microorganisms ubuitous
- Small size
- Rapid reproduction
- Metabolic diversity
Aflatoxins
Flat-ringed, planar compounds that can intercalate between bases of DNA and act as mutagens, carcinogenic (from Aspergillus flavus)
Myxobacteria (Myxococcus xanthus)
Gram - rod-shaped bacteria, found in soil and plant residue
* Very social, predatory, binary fission
* Flexible cell wall, utilizes gliding motility to “ripple” across a surface
* Forms fruiting bodies from vegetative cells upon starvation, in which dormant myxospores are formed and can germinate in nutrient-rich conditions
Phylum Actinobacteria
Aerobic, Gram +, with high GC (“actinomycetes”)
* Produce hyphae and mycelium, which give rise to conidiospores
* Leathery culture formed from aerial (conidiospores) and submerged mycelium
* Ex. Streptomyces
Streptomyces
An actinomycete found in the microflora of most soils
* Produces the chemical (geosmin) causing earthy scent of moist soil following rain (petrichor)
* Produces over 10,000 bioactive compounds, serving as major sources of antibiotics
Cyanobacteria
Gram - bacteria, perform oxygenic photosynthesis
* Contain chlorophylls
Green and Purple Bacteria
Carry out anoxygenic photosynthesis using other reduced compounds as e- sources
* Contain bacteriochlorophylls
Photosynthetic bacteria utilize accessory pigments such as ____ and ____ to optimize light harvesting across the visible spectrum
phycobiliproteins, carotenoids
Rhodospirillum rubrum
A photosynthetic, purple nonsulfur bacterium
* Observed spiral motility under phase-contrast and darkfield
Winogradsky Column
An artificial microbial ecosystem in which microorganisms and nutrients interact over a vertical gradient
Winogradsky column vertical bacteria breakdown
Top (high O, low S)
Algae
Cyanobacteria
Sulfur-oxidizing bacteria
Purple non-sulfur bacteria
Purple sulfur bacteria
Green sulfur bacteria
Anaerobic bacteria
Bottom (low O, high S)
By adding chemicals to a minimal medium, it is possible to ____ the growth of interfering microbes, or ____ the growth of the sought-after microbe
repress (repressive selection), encourage (enrichment selection)
Differential plating
Making isolations of target colonies grown from a repressive/enrichment selection to ascertain the purity of the culture
Escherichia coli
Gram - rod, resides in lower intestinal tract
* Motile, no endospores
Enterococcus faecalis
Gram + cocci, resides in lower intestinal tract
* Non-motile, no endospores
Staphylococcus (from face swab)
Gram + cocci, resides on mammalian skin and in sand or water plants
* Non-motile, no endospores
Bacillus
Gram + rods, resides in soil
* Motile, produces endospores, isolated via heating
Pseudomonas
Gram - rods, resides in soil
* Motile, no endospores
Azotobacter
Gram -, large, ovoid rod-shaped, resides in soil
* Motile/non-motile strains, produces cysts
MacConkey’s (MAC) agar and Eosin Methylene Blue (EMB) agar
- Selective and differential media
- Selects for Gram - bacteria
- Differentiates bacteria that ferment (pink) and don’t ferment (yellow) lactose
DNase Test Agar
Establishes a distinction between Serratia and S. aureus (DNase+) from Escherichia and Enterobacter (DNase-), as they produce extracellular deoxyribonucleases indicated with a violet-colored zone
Catalase Test
Tests for the presence of catalase by the decomposition of hydrogen peroxide (H2O2) to water and O2
* Observed as bubble formation in + (Staphylococcus), no reaction in - (Streptococcus)
Oxidase Test
Tests for cytochrome oxidase (heme-containing protein used via e- transport in some bacteria)
* Produces purple color if + (Azotobacter, Pseudomonas), colorless if - (Escherichia, Staphylococcus, Enterococcus, Streptococcus)
Indole Test
Tryptophan can be broken down to indole by some bacteria, detected by Kovac’s reagent to a culture in tryptone broth
* Non-selective, used to separate enterics (E. coli, +) from Enterobacter (indole -)
