Microbiology Chapter 6 Flashcards
Bacterial binary fission 4 step description?
Cell elongation and dna replication
Cell wall and plasma membrane constrict
Cross walls seperate two copis of dna
Cell seperation
Microbial growth refers to
Number of cells not cell size
Which Fts protein = filamentous temperature sensitive found in prolaryotes mitochondria abd chloroplast is important for ?
Cell divsion because they form a divisome
Other ftsz functions
Attracts other ftsz tp form ring
Ftsz depolymerizes
Hydrolyze gtp for energy
Assembly of polymers occurs outside the cytoplasmic membrane. What enzyme cuts and insert peptidoglycan
Autolysins
Lipid carrier molecules known as bactoprenol transport building blocks across the membrane, what building blocks do they transfer
: NAG/NAM/pentapeptide
what is the bactoprenol mechanism
Carrier inserts the building block into the glycan backbone, then moves back inside the cell to pick up another building block
what process involves Initially 2 alanine residues at the end of the peptidoglycan precursor
One splits off during transpeptidation
Bond between two Ala residues activates subterminal D-Ala, favoring reaction with DAP
No energy outside membrane - transpeptidation replaces requirement for energy
transpeptidation
how to find generation time and number of generations
of generations =Log number of cells (end) − Log number of cells (beginning)/ Log number of 2
generation time = (60 min x # of hours)/number of generations
four parts of a bacterial growth curve called
- Intense activity preparing for population growth, but no increase in population.
- Logarithmic, or exponential, increase in population.
- Period of equilibrium; microbial deaths balance production of new cells.
- Population Is decreasing at a logarithmic rate.
- Lag Phase
- Log phase
- Stationary Phase
- Death Phase
Direct or Indirect method of measuring bacterial growth
Plate counts
Filtration
MPN
Direct microscopic count =petroff hausser cell counter
Direct
Direct or Indirect method of measuring bacterial growth
Turbidity =light sensitive detector
Metabolic activity
Dry weight
Indirect
two methods for preparing plates for counting
Pour and spread plate methods
Temperature, PH osmostic pressure are physical or chemical contraints for growth?
physical
Carbon Nitrogen, sulfur, and phosphorous Trace elements Oxygen Organic growth fact are physical or chemical contraints for growth?
chemical
temperature range for General danger zone for bacteria
150-30F an 63 to 0C
pychrophily or thermophily
Enzymes function optimally in the cold
Denatured or inactivated at higher temperatures
More -helix and less -sheet
More polar and fewer hydrophobic amino acids
Active transport occurs at low temperatures
Cytoplasmic membranes contain higher content unsaturated fatty acids
Maintain semi-fluid state at lower temp
Some lipids also contain polyunsaturated fatty acids and long chain hydrocarbons with multiple double bonds
pychrophily
pychrophily or thermophily
Enzymes and other proteins stable to heat
Critical amino acid substitutions
Increased number salt bridges
Densely packed highly hydrophobic interiors of proteins
Protein synthesizing machinery and structures such as cytoplasmic membrane are also heat stable
Membranes rich in saturated fatty acids
Form stronger bonds than unsaturated fatty acids
thermophily
Microbe PH ranges
Most bacteria grow between pH 6.5 and 7.5
Molds and yeasts grow between pH 5 and 6
Acidophiles grow in acidic environments
Critical factor in growing in non-neutral pH is cytoplasmic membrane
Hypertonic environments, or an increase in salt or sugar, cause plasmolysis
Extreme or obligate halophiles require high ____
Facultative halophiles tolerate high _____
Osmostic pressure
Effescts of ocygen on growht of bacteria
powerpoint chapter 6 page 35
Reducing media
Contain chemicals (thioglycolate or oxyrase) that combine O2
Heated to drive off O2 examples?
candle jar and anaerboic chamber
what bacteria requires Microbes that require high CO2 conditions
CO2 packet
Candle jar
Capnophiles
characteristics of biolfilms: like biolfilms in the mouth
Microbial communities Form slime or hydrogels Bacteria attracted by chemicals via quorum sensing Share nutrients Sheltered from harmful factors
Culture medium: nutrients prepared for microbial growth
Sterile: no living microbes
Inoculum: introduction of microbes into medium
Culture: microbes growing in/on culture medium
culture media terms
Chemically defined media: exact chemical composition is known
Complex media: extracts and digests of yeasts, meat, or plants
Nutrient broth
Nutrient agar
culture media
Complex polysaccharide Used as solidifying agent for culture media in Petri plates, slants, and deeps Generally not metabolized by microbes Liquefies at 100°C Solidifies at ~40°C
agar
Make it easy to distinguish colonies of different microbes? Differential, Selective and Enrichment
Differential
Suppress unwanted microbes and encourage desired microbes?Differential, Selective and Enrichment
Selective
Encourages growth of desired microbe
Assume a soil sample contains a few phenol-degrading bacteria and thousands of other bacteria
Only phenaol metabolizing will be growing?
Enrichment
A colony is a population of cells arising from a single cell or spore or from a group of attached cells
A colony is often called a
Colony forming unit CFU
explain the biosafety levels 1-4
BSL-1: no special precautions BSL-2: lab coat, gloves, eye protection BSL-3: biosafety cabinets to prevent airborne transmission BSL-4: sealed, negative pressure Exhaust air is filtered twice
