Microbiology – Lect. 21-25 (ecology/biotech) – Flashcards

always on

Production of: light, virulence factors, and biofilm; energy costly!

1. molecule is always inside and is diffused out.
2. once population density is high enough, QSM diffuses back inside and is represented

ex. Vibrio fischeri

environments are not constant

microbes prefer to form on surfaces

Competition

predation/parasitism:  Bdellovibri

Synergism/mutualism: dental biofilms

Rapid growth vs. survival

 Lab generation time vs. nature gen. time

Siderophores (Fe)

Active transport via specific binding proteins

chemotaxis

motility: actin "rockets"

organisms selected for survival (evolution)

Dissapearance of food

Appearance of byproducts (acid/NO₃)

radioactive substrates: tagged sugars

Fluorescent In Situ Hybridization

specific or general probes used

Mimic environmental condition in Lab

Wingradsky Column (core sample) for sedimentorgansims

physical, chemical, biological properties

ecology= interactions within environment

Root-surface organisms: Rhizospheres (symbiotic)

Plant Diseases: Agrobacterium tumefaciens; induces opine production

Hydrothermal vent: worms with bacteria

Aquifer and subsurface

Microbes can cycle:

Carbon, Nitrogen, Phosphorous, Iron, Sulfur

Nitrogen required for:

protein synthesis

nucleic acid synthesis

other cell components

N₂ = 78% atmosphere: microbes use NO₃^- / NH₃ / R-NH₂

N₂ → NH₃

Enzyme: Nitrogenase 

highly regulated; energy extensive (16 ATP/N₂)

O₂ sensitive (no O₂ present)

NO₃^• → N₂ or NH₃

most common

Nitrate used as final electron acceptor

 CO₂ → organic Carbon

 CO₂ major reservior of carbon

 CO₂ fixation done by primary producers; Autotrophs (photosynthetic and lithotrophs)

Organic Carbon → CO₂

Sugar/protein/lipid decomposition

carbon trapped in complex molecules; cellulose, lignan

 H₂S → elemental sulfur

 Beggiatoa, Thiothri

 H₂S → SO₄^2-

 Thiobacillus

 SO₄^2- → S₂^-

SO₄^2- is used as an electron acceptor; "dissimilatory sulfate reduction"

ex: Desulfovibrio / some Clostridium sp.

SO₄^2- can also be used as a sulfur source; "assimilatory reduction"

 Ocean water range: -2° → 100° (most below 5°C)

Deep sea thermal activity

growth on ice as well

Barotolerant and Barophilic

most = psychrophiles (grow in extreme conditions)

photosynthetic organism live in Photic Zone 

Turbidity impacts range of photic zone

Range: 0% (fresh) – 3.7% (sea)

Saturated = Great Salt Lake 32%

Halotolerant and Halophilic

different levels impact community composition

Laguna Diamante

– pH 11

– 5X salt concentration

– 20,000X arsenic

– High UV, low O2

microbes and flamingos

Water can be a pathogen reservoir;

V. cholerae, Shigella, Salmonella, some E. coli

Detection is key; pathogens at low levels

1. be present only in polluted H2O
2. be present when pathogens are present
3. # of IOs correlate with pollution level
4. Survive longer than pathogen
5. Uniform & Stable properties
6. be "harmless" to animals/humans
7. be present in greater # than pathogen
8. Relatively easy to detect

E. coli is the most common:

Coliform: a Gram negative, lactose fermenting rod; 

normal inhabitant of the intestinal tract

 Streptococcus faecalis also used

High Coliform counts = water is not potable, lakes closed

 Filtration: removes particulates

Treatment with chlorine: kills microbes

Optional:

Reverse osmosis or charcoal filtration; Remove chemical contaminants

BOD= Term for O₂ consumption over 5 days

Organic matter dumped into water = problem

aerobic microbes deplete oxygen

Bad: food spoilage, food-borne infections

Good: fermentations (beer, cheese, etc.), occasionally microbe is eaten (yogurt)

Food/beverage= Culture media

Good: milk eggs meat

Bad: flour, sugar, cereal (dry), vinegar (low pH)

Initial # of microbes present

Processing/sterilization of food and/or equipment

Damage to containers

Storage conditions

 Metabolites produced may be harmful;

– Neurotoxin from C. botulinum

– Enterotoxin from S. aureus

Can cause infection;

– E. coli, Salmonella, L. monocytogenes

Used for: milk, eggs, crabmeat, beer, wine, cheese

Milk pathogens: M. bovis, L. monocytogenes

Check for milk coliforms (determine fecal contamination)

Microwave ovens: ineffective (uneven heating)

Refrigeration; bacteriostatic,

Produce: heated before freezing; inactivates oxidase enzymes that alter food quality

High salt or sugar content is bacteriostatic; salted fish/jams

*still prone to fungal contamination

Add flavor and cover ‘off’ flavors

enhances preservation

Organic acids (sorbic, lactic, citric) control growth 

of molds and bacteria

Nitrates and nitrites inhibit growth, also 

contribute to “redness” of meat;

Raises concern about carcinogenic effect

Foods exposed to UV or gamma radiation

Will either pasteurize or sterilize food; exposure dependent

Microbes can be grown in batch or continuous culture:

Conditions must be monitored closely;

– Aeration, temperature, pH

Saccharomyces cerevisiae; used for bread

Developing Strains:  

Alcohol tolerance (normal 8-9%)

speed/purity of alcohol production

ability to flocculate (loosely coagulate)

growth rate

Glucose enters glycolysis

Glucose→ G6P→F6P→→→Pyruvate

Pyruvate→ acetyl CoA→ Krebs cycle

Pasteur Effect: cell growth, 0 EtOH production

Pyruvate → acetyl CoA + CO₂ → Ethanol

Enzyme 1: pyruvate decarboxylase

Enzyme 2: alcohol dehydrogenase

0 cell growth, EtOH production

If O₂ is present, ethanol can be oxidized to 

acetic acid by Acetobactre spp.

Curddling of milk: 4.6 pH

Lactic acid byproduct; enhances taste and preservation

Examples: Buttermilk, yogurt, cottage cheese, cheddar cheese, cream cheese