TBL Flashcards
What is gram-negative bacteria
- bacteria that do not retain the crystal violet stain used in the gram-staining method => appears red/pink
- cell envelopes composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane
V. natriegens is a halophile, what is halophile?
organism that thrives in or can tolerate saline conditions
What are V. natriegens natural habitats
- brackish water
- estuarine mud
what is brackish water
- water with salinity levels between seawater and freshwater
- may occur as estuaries or brackish fossil aquifers
what is estuarine mud
the mud of the waters where seawater and freshwater meets
V. natriegens are not photoluminescent, what are photoluminescent bacteria?
- light-producing bacteria
- predominantly present in sea water, marine sediments, the surface of decomposing fish and in the gut of marine animals
- free living or in symbiosis with animals: hosts provide safe home and nutrition. Hosts use the light produced by the bacteria for camouflage, prey and/or mate attraction
- luminescence reaction could also be for quorum sensing: ability to regulate gene expression in response to bacterial cell density
Is V. natriegens free living, parasitic or mutualistic with other animals?
free living
How do V. natriegens move?
by single polar flagellum
What is a single polar flagellum
- single flagellum at one pole
How is V. natriegens shaped?
comma-shaped vibrio
What are the metabolic characteristics of Vibrio species?
facultatively anaerobic heterochemoorganotrophs
what is a faculative anaerobe
can survive in the presence of oxygen, can use oxygen in aerobic respiration, but can also survive without oxygen via fermentation or anaerobic respiration.
what is a heteroheterochemoorganotroph
- cannot produce its own food
- energy source: breaking down organic chemical compound
- obtain electrons or hydrogen from the organic compounds
- uses organic sources of carbon
Are Vibrio species cyt-c oxidase positive or negative (TMPD test)? And what does that mean?
- positive => purple colour
- cyt-c oxidase positive organisms contain cytochrome c as part of their respiratory chain
- organisms lacking cytochrome c as part of their respiratory chain do not oxidise the reagent, leaving it colorless => negative
Are Vibrio species catalase positive or negative in H2O2 test and what does that mean?
- usually catalase positive => bubbles when H2O2 added
- Test is used to identify organisms that produce catalase: detoxifies hydrogen peroxide by breaking it down into water and oxygen gas
what do Vibro species do when under aerobc conditions
oxidise glucose fully to carbon dioxide using oxygen
What do Vibrio species do under anaerobic conitions?
- respire using nitrate rather than oxygen as a terminal electron acceptor. Therefore they are nitrite positive (forms red precipitate) in sulfanilic acid / α-naphthylamine test because nitrate is reduced to nitrite
- most can also use glucose anaerobically by mixed acid fermentation, producing lactate, succinate, etc., but not usually ethanol, CO2 or H2. Therefore have a positive methyl red test
what is methyl red test
- used to determine which fermentation pathway is used to utilize glucose
- In mixed acid fermentation pathway, glucose is fermented and produces several organic acids (lactic, acetic, succinic, and formic acids)
- stable production of enough acid to overcome the phosphate buffer will result in a pH of below 4.4. If the pH indicator (methyl red) is added to an aliquot of the culture broth and the pH is below 4.4, a red color will appear => positive
- negative = yellow
Vibrio species sources of nitrogen?
both organic and inorganic (NH4+, NO3−)
what is a defined media
media that contain specific amounts of pure, chemically defined ingredients e.g. NaCl
What is complex media
media that contain at least one ingredient that is a mixture of ill-defined components (peptides, sugars, vitamins, etc.) of unknown proportions
in what conditions is the media autoclaved at?
121°C for 15 min at 15 psi (103 kPa)
what is autoclaving
usesing steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel
why does autoclaving have to be at 121°C and not just boiling temperature?
bacterial spores can survive 100°C
Why does the pressure in autoclave have to be raised to 15 psi
so that the water doesn’t boil until it reaches a temperature high enough to kill bacterial endospores
V. natriegens is non-fastidious heterotroph, what does that mean?
organism that does not require special nutrients to be present in their culture medium to grow
what does the defined media of non-fastidious heterotroph often contain?
- phosphate: pH buffer and phosphorus source
- salt: regulate ionic strength
- carbon source (usually a sugar, but amino acids can also be used)
- nitrogen source (e.g. ammonium, nitrate, or glutamate)
- various trace elements (Mg, Ca, Fe, Cu, etc.)
what do fastidious microbes additionally need on top of the usual components of non-fastidious defined media
additional trace elements (Fe, Zn, Co, Mo, Cu, B, etc.), vitamins, amino acids, etc.
what is the preferred complex medium for V. natriegens
- BHI (brain-heart infusion) broth
- BHI is made by combining an infusion from boiled bovine or porcine heart and brain with a variety of other nutrients
- 37 g·L−1 brain-heart infusion
- 20 g·L−1 NaCl
what is M9Na
A modified version (for halophilic V. natriegens) of the common defined medium for non-fastidious heterotrophs M9
