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Bacteriology > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Essential nutrients

A

-are those that must be supplied from the environment.

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2
Q

Macronutrient

A
  • Major elements in cell macromolecules- C, O, H, N, P, S

- Ions necessary for protein function- Mg2+, Ca2+, Fe2+, K+

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3
Q

Micronutrients

A
  • Trace elements necessary for enzyme function

- Co, Cu, Mn, Zn, and others

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4
Q

Autotrophs

A
  • fix CO2 and assemble it into organic molecules.
  • Photoautotrophs
  • Chemoautotrophs (or lithotrophs)
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5
Q

Phototrophs

A

-obtain energy from light, transformed into chemical energy

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6
Q

Heterotrophs

A
  • use preformed organic molecules that originated from autotrophs.
  • Photoheterotrophs
  • Chemoheterotrophs (or organotrophs)
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7
Q

Chemotrophs

A
  • obtain energy from chemical oxidation-reduction reactions
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8
Q

Lithotrophs

A
  • use inorganic molecules as a source of electrons
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9
Q

Organotrophs

A
  • use organic molecules
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10
Q

Energy Is Stored for Later Use

A
  • A membrane potential is generated when chemical energy is used to pump protons outside of the cell.
  • The H+ gradient plus the charge difference form an electrochemical potential, called the proton motive force (PMF).
  • The potential energy stored in the PMF can be used to transport nutrients, drive flagellar rotation, and make ATP by the F1FO ATP synthase.
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11
Q

The Nitrogen Cycle

A
  • Nitrogen fixers possess nitrogenase, the enzyme that converts N2 to ammonium ions (NH4+).
  • Nitrogenase is destroyed by oxygen
  • Nitrifiers oxidize ammonia to nitrate (NO3–).
  • Denitrifiers convert nitrate to N2
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12
Q

Nitrogen-fixing bacteria

A
  • may be free-living in soil or water, or they may form symbiotic associations with plants.
  • Rhizobium bacteria are symbionts with leguminous plants such as soybeans, chickpeas, and clover
  • The root nodules produce the microoxic environment required by the nitrogenase enzyme
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13
Q

Selective permeability

A
  • Substrate-specific carrier proteins, or permeases
  • Dedicated nutrient-binding proteins in the periplasmic space
  • Membrane-spanning protein channels or pores
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14
Q

Facilitated diffusion

A
  • helps solutes move across a membrane from a region of high concentration to one of lower concentration.
    -Is selective for specific molecules
    -It does not use energy and cannot move a molecule against its gradient.
    Example: the aquaporin family that transports water and small polar molecules such as glycerol
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15
Q

Coupled transport systems

A
  • energy released by an ion moving down its gradient is used to move a solute up its gradient.
  • In symport, the two molecules travel in the same direction.
  • In antiport, the two molecule moves in opposite directions
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16
Q

ABC transporters

A
  • largest family of energy-driven transport systems is the ATP-binding cassette superfamily
  • found in all three domains of life
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17
Q

ABC transporters- Two main types

A

Uptake ABC transporters

  • are for transporting nutrients into the cell.
  • Use a periplasmic solute-binding protein

Efflux ABC transporters
-which include multidrug efflux pumps

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18
Q

Group translocation

A

-a type of active transport that uses energy to chemically alter the substrate during its transport.

19
Q

phosphotransferase system (PTS)

A
  • type of Group translocation
  • example present in many bacteria.
  • It uses energy from the metabolite phosphoenolpyruvate (PEP) to attach a phosphate to specific sugars.
  • The phospho-sugar cannot leak back out of the cell, and is ready to be metabolized
20
Q

two main types of culture media used to grow bacteria

A
  1. Liquid, often called broth
    - Useful for studying the growth rate and for obtaining cell mass for study, industry, or biotechnology
  2. Solid (usually gelled with agar),
    useful for:
    -Separating species from mixed cultures from clinical specimens or natural environments
    -Counting colonies, each from a single cell
    Observing differential growth characteristics
21
Q

Colonies are isolated via two main techniques

A
  1. Streaking
    - Dragging a loop across the surface of an agar plate
    - Diluting the sample to obtain single isolated colonies
  2. Spread plate
    - Tenfold serial dilutions are performed in liquid culture medium
    - A small amount of each dilution is then “plated”, spread on a plate of solidified medium
    - Goal is to find a dilution that produces isolated colonies
22
Q

Growth Factors

A
  • specific nutrients required by some organisms include certain vitamins and amino acids.
  • These growth factors must be available in growth medium
  • examples of some organisms that require specific growth factors include staphylococcus and mycobacterium
23
Q

pure culture

A
  • Microbes in nature exist in complex, multispecies communities
  • for detailed studies they must be grown separately
24
Q

Complex media

A
  • are nutrient rich but poorly defined.

- might contain yeast or beef extract, protein mix, etc.

25
Q

Synthetic media

A
  • made from specific chemicals such as salts, glucose or other sugars, specific amino acids, etc.
  • A defined minimal medium contains only the compounds needed for an organism to grow.
26
Q

Enriched media

A

-complex media to which specific components such as blood are added to support growth of certain bacteria

27
Q

Selective media

A

-favor the growth of some organisms over others, so the organisms of choice are not obscured by the presence of numerous other organisms.

28
Q

Differential media

A

-produce visible differences between two species that grow equally well, so each type can be counted

29
Q

Direct Counting of Living and Dead Cells

A
  • Microorganisms can be counted directly by placing dilutions on a special microscope slide and examination with a microscope.
  • But you cannot tell if a cell is living or dead
30
Q

Fluorescence-Activated Cell Sorter (FACS)

A
  • Stained fluorescent cells are passed through a small orifice, one cell at a time, and then past one or more lasers.
  • Some detectors measure light scatter to determine the number and size of all cells.
  • Other detectors measure fluorescence
31
Q

Other Techniques for Counting

A
  • A viable (living) bacterium can replicate and produce a colony on a solid medium.
  • Viable cells can be counted via the spread plate (cells on top of the agar) or pour plate (cells mixed in the agar) methods
  • Microorganisms can be counted indirectly via biochemical assays of cell mass, protein content, or metabolic rate.
  • Used for biotechnology
  • Measuring the optical density (OD) of a bacterial liquid culture or suspension with a spectrophomometer is often the fastest and easiest way of determining the number of bacteria.
  • Direct relationship between OD and number of cells
32
Q

binary fission

A
  • the way most bacteria divide
  • one parent cell splits into two equal daughter cells.
  • some divide asymmetrically
33
Q

Growth rate

A
  • rate of increase in cell numbers or biomass of a bacterial culture
  • Rapid bacterial growth is called “exponential” because it generates an exponential curve, a curve whose slope increases continually.
  • Cell numbers double every time interval
  • If a cell divides by binary fission, the number of cells in a culture is proportional to 2n, where n = number of generations
34
Q

Generation Time

A

-the time it takes for a population to double
-For cells undergoing binary fission,
Nt = No x 2n
Nt= is the final cell number
No= is the original starting cell number
n= is the number of generations, which is the time of growth divided by the generation time.

35
Q

batch culture

A
  • simplest way to model the effects of a changing environment is to culture bacteria
  • A liquid medium within a closed system
  • changing conditions in this system greatly affect bacterial physiology, gene expression, and growth.
  • The bacteria adapt to the changing environment by changing their gene expression and metabolism.
36
Q

Stages of bacterial Growth

A

Lag phase- no growth because cell have to adjust to the new environment
Log phase- doubling every unit of time
Stationary phase- all nutrients are used and no more growth can occur
Death phase- lack of nutrients and build up of waste products causes death

37
Q

continuous culture

A
  • all cells in a population achieve a steady state, which allows detailed study of bacterial physiology.
  • A chemostat apparatus ensures logarithmic growth by constantly adding and removing equal amounts of culture media.
38
Q

biofilms

A
  • many bacteria formspecialized, surface-attached communities
  • usually contain multiple species, and can form on a range of organic or inorganic surfaces.
  • form and continue to grow when nutrients are plentiful.
  • Once nutrients become scarce, individuals detach from the community to disperse in search for new sources of nutrients.
  • in nature can take many different forms and serve different functions for different species.
  • The formation involves chemical signaling between organisms.
39
Q

steps in the formation of many kinds of biofilms

A
  1. Attachment
  2. Microcolonies
  3. Exopolysaccharide (EPS) production - material that helps them stick together
  4. Mature Biofilm
  5. Dissolution and dispersal
40
Q

Cell Differentiation

A
  • Bacteria faced with environmental stress undergo complex molecular reprogramming that can include changes in cell structure.

Examples include:

  • Endospores of Gram-positive bacteria
  • Heterocysts of cyanobacteria
  • Fruiting bodies of Myxococcus xanthus
  • Aerial hyphae of Streptomyces
41
Q

Endospores

A

Clostridium and Bacillus species can produce dormant spores that are heat resistant.

Starvation initiates an elaborate 8-hour genetic program that involves:

  • An asymmetrical cell division process that produces a forespore and ultimately an endospore
  • mother cell engulfs the forespore which is now surrounded by a cortex which protects it from heat

Sporulation can be divided into discrete stages based primarily on morphological appearance

42
Q

Cyanobacterial Heterocysts

A

Allow this multicellular organism to fix nitrogen anaerobically in the heterocyst while maintaining oxygenic photosynthesis in vegetative cells

43
Q

Fruiting Bodies

A
  • Myxococcus xanthus uses gliding motility

- Starvation triggers the aggregation of 100,000 cells, which form a fruiting body containing myxospores

44
Q

Filamentous Structures

A
  • Streptomyces bacteria, a major source of antibiotics, form mycelia and sporangia analogous to those of fungi
  • As nutrients decline, aerial hyphae divide into spores that are resistant to drying

Bacteriology (16 decks)

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