Chapter 4 How Microbes Grow

Question 1

Phosphototransferase System

Answer 1

-It contains both cytoplasmic and cell membrane components -It requires energy expenditure -It transfers a phosphate group to sugar

Question 2

Biofilms (quiz question)

Answer 2

• Can have single or multiple species of bacteria
• May cause health problems for humans

–Bladder catheters: 10-30% increase infection risk

–Dental implants: 5-10%

–Central venous catheters: 3-%

–Cardiac pacemakers: 1-5%

–Joint prostheses: 1-3%

Question 3

For a bacterium to uptake glucose against its concentration gradient…

Answer 3

The bacterium will require a glucose transport protein and will also expend energy.

Question 4

Which of the following is true of quorum sensing?

Answer 4

-It involves a sufficient cell density or “quorum” of cells -It is important for regulation of genes involved in biofilm formation, among other functions (virulence, bioluminescence, etc..) -It involves cell to cell “communication” using chemical signaling

Question 5

Under optimal conditions one E. Coli cell can become two cells every…

Answer 5

Every 20 to 30 minutes

Question 6

Which of the following is true with respect to cell differentiation:

Answer 6

Bacteria can undergo cell differentiation in response to an environmental stress

Question 7

Siderophores are responsible for helping bacteria aquire

Answer 7

iron

Question 8

Which of the follow is NOT a macronutrient? A. Copper B. Phosphorous C. Oxygen D. Carbon

Answer 8

A. Copper

Question 9

Nitrogen fixing bacteria (diazotrophs):

Answer 9

Can convert atmospheric nitrogen (N2) into ammonia

Question 10

Which of the follow is true of complex media:

Answer 10

Bacteria generally grow quickly on it compared to defined synthetic media

Question 11

With respect to counting cells, a “viable” bacterium is one that:

Answer 11

Can replicate and form a colony on a solid media surface

Question 12

Cyanobacteria are an example of

Answer 12

Photoautotrophs

Question 13

Differential medium containing specific inhibitors such as bile salts and/or crystal violet (such as MacConkey medium or EMB agar) selects for which type of bacteria:

Answer 13

Gram-negative bacteria

Question 14

Match the following descriptions to the appropriate phase of growth shown in the graph below (A, B, C, or D):

Answer 14

A. Lag phase where cells are adjusting to the new medium and synthesizing proteins necessary for growth

B. Log phase where cells are growing rapidly and the cell number doubles (2->4->8->16, etc.) within a time period termed the “doubling time”

C. Stationary phase where cells are growing and dying at relatively equal rates, neither of which is very fast

D. Death phase where cells are slowly dying

Question 15

Passive transport

Answer 15

when molecules move through the membrane without using energy

diffusion and porins

Question 16

Active Transport

Answer 16

• requires energy to move molecules across the membrane
• ABC type
• Coupled active transport
  
  • symport (2 molecules same way) and antiport (one molecule one way, one the other)

Question 17

Facilitated Diffusion

Answer 17

helps solutes move acorss a membrane from a region of high concentration to one of lower concentration

Question 18

Phosphotransferase System (PTS)

Answer 18

Energy from glycolysis –> used to phosphorylate Mannitol, glucose, mannose

Question 19

Complex “undefined media”

Answer 19

Example: yeast extract, beef extract, peptonized meat (peptone), proteose-peptone, tryptone, blood agar, casamino acids

Grows “weeds” - E. coli and easy to grow bacteria

Example: nutrient broth

Question 20

Defined media

Answer 20

You know what the majority of the ingredients are (defined)

Example: Salt/major trace metals, C, N, P and S

Question 21

Differential Media

Answer 21

Distinguise between types of organisms

Many types can grow

example: pH indicators

Question 22

Selective Media

Answer 22

Select for the growth of only certain types of organisms - intentially prohibit growth of some groups

Example: acid, alkaline, bile salts

NOTE: all media is unintentionally selective

“expose biochemical differences between two species that grow equally well”

Question 23

EMB agar - Eosin Methylene Blue

Answer 23

Differential medium: Methylene blue precipitates from acid produced by Lac + colonies

Lac + colonies are dark green shimmery

Crystal violet inhibits G+ves = ______

Question 24

MacConkey Agar

Answer 24

Bile salts favor Gram - enteric organisms

contains bile salts and crystal violet

also includes lactose, neutral red, and peptones to differentiate lactose fermentors from non-fermentors

Allows one to distinguish Lactose fermentors (Lac +) from non (Lac -) acid producers (like E. Coli) turn red on the plate (dye seeps into the cells)

BOTH: A. Selective and B. Differential

Question 25

Law of the Minimum

Answer 25

Elements present in distinct proportions

Total biomass determined by the nutrient present in the lowest (minimum) concentration

Popularized by Justus von Liebig (1803 - 1873) but first described by Karl Sprengel (1787 - 1859)

Question 26

How do you ensure cells will replicate?

Answer 26

Make sure you put them into the environment they are used to

Make sure you take them from log phase and put them in new environment

Question 27

Great Plate Count Anomaly

Answer 27

Orders of magnitude increase cell numbers microscopically vs. culture-based

• we can culture <.1-.01% of the total species
• culture independent vs culture based

Question 28

What is a biofilm?

Answer 28

Surface attached to microbial community in a protective matrix

• protects against dispersion
• protects from antibodies, phagocytes, and antibodies
• protects from temperature, pH, and environmental stressors
• cells signal to each other via quorum sensing
• most biofilms are formed in nature
• multiple of single species
• ECM: polysaccharides, proteins, and DNA
  ex. iron mtn comprised mainly of archaea

Question 29

Biofilm development

Answer 29

Tunnels b/w mushrooms –> nutrient exchange

Planktonic vs. biofilm cells

Changes in gene regulation

Question 30

Biofilm cells vs. Free-swimming cells

Answer 30

Genetically identical

Gene expression is vastly different

EC polysaccharide adn adhesin genes expressed in biofilms

other types of biofilm-specific gene expression (cannibals/polysaccharide producers/quorum sensing)

Flagella production genes turned off in biofilms

Question 31

Diagram of a Medical Biofilm

Answer 31

Resistant to antibiodies, white blood cells, and antibiotics (unlike planktonic cells)

Phagocytes release enzymes that damage surrounding tissue

Planktonic bacteria may cause infection in neighboring tissue

A. Planktonic bacteria can be cleared by antibodies and phagocytes and are susceptible to antibiotics

B. Adherent bacterial cells form biofilms, preferentially on inert surfaces and these sessile communities are resistant to antibodies, phagocytes, and antibiotics

C. Phagocytes are attracted to the biofilms. Phagocytosis is frustrated but phagocytic enzymes are released.

D. Phagocytic enzymes damage tissue around the biofilm, and planktonic bacteria are released from the biofilm. Release may casue dissemination and acute infection from neighboring tissue

Question 32

Quorum Sensing

Answer 32

Biofilms use them to communicate

Complex regulation system involving small inducer molecules (AHL)

When there are enough bacteria (a quorum) they will do “something”

Question 33

Example of Bioluminescence

Answer 33

Vibrio fischeri: a luminescent symbiont in the Hawaiian bobtail squid light organ

Question 34

Endospore formation by Gram + bacteria

Answer 34

Examples: Clostridium botulinum, Bacillus anthracis

Question 35

Cell Differentiation: Sporulation

Answer 35

Example: Bacillus subtilis

Question 36

Spore Longevity Example

Answer 36

Guinard Island in Scotland

B.anthracis biological weapons released in 1942 (WW2II)

Virulent Bacillus spores remained for 50 years

Decontaminated in 1990 w/ 280 tons of formaldehyde

Some endospores can last for 9,000 years!

Question 37

photoautotrophy

Answer 37

generates energy through light absorption by the photolysis (light-activated breakdown) of H20 or H2S. The energy used to fix CO2 into biomass.

Question 38

Chemoautotrophy

Answer 38

aka lithotrophy

Produces energy from oxidizing inorganic molecules such as iron sulfur, or nitrogen. This energy is used to fix CO2 into biomass

Question 39

Heterotrophs

Answer 39

Breakdown organic compounds from other organisms to gain energy and to harvest carbon for building their own biomass.

Heterotrophic metabolism can be divided into two classes based on whether light is involved

Question 40

photoheterotrophy

Answer 40

produces energy through photolysis of organic compounds or via a light-powered proton pump

Organic compounds are broken down and used to build biomass

Question 41

Chemoheterotrophy

Answer 41

aka organotrophy

Yields the energy and carbon for biomass solely from the organic compounds.

Chemoorganotrophy is commonly called heterotrophy

Question 42

Autotroph

Answer 42

build biomass by fixing CO2 into complex organic molecules through one of two general metabolic routesthat either use or ignore light

Question 43

chemolithotroph

Answer 43

oxidize inorgani chemicals ( for example, H2, H2S, NH4+, NO2-, and Fe2+

one type of chemotrophic organism (other type is organotrophs)

Question 44

Symport

Answer 44

Coupled transport where molecules travel the same direction

Question 45

Antiport

Answer 45

Coupled transport where the molecules travel the opposite direction

Question 46

Electrogenic Pump

Answer 46

Unequal distribution of charge results

Example: LacY proton-driven transport

Example: symport of a neutral lactose molecule with H+ results in net movement of positive charge

Question 47

ABC Transporters

Answer 47

ATP-binding cassette superfamily energy driven transport system

Found in bacteria, archaea, and eukaryotes

Critical for transporting nutrients such as maltose, histidine, arabinose,, and galactose

Efflux ABC transporters are gnereally used as multidrug efflux pumps that allow microbes to survive exposures to hazardous chemicals

Consists of two types of hydrophobic proteins that form a membrane channel and two peripheral cytoplasmic proteins that contain a highly conserved amino acid sequence

Question 48

SIderophores

Answer 48

Type of ABC transporters

Have a very high affinity for whatever soluble ferric iron is available in the environment

Produced and sent forth whenever the intracellular iron is low

In Gram - organisms, it binds to iron and then the new complex attaches to specific receptors in the outer membrane

Question 49

Growth Rate

Answer 49

Rate of increase in cell numbers or biomass

Proportional to the population size at a given time