WEEK 2 (part II): BACTERIAL GROWTH, NUTRITION, METABOLISM, AND GENETICS Flashcards
energy source: light
carbon source: CO2
Photoautotroph
energy source: light
carbon source: organic compounds
Photoheterotroph
energy source: chemical
carbon source: CO2
Chemoautotroph
energy source: chemical
carbon source: organic compounds
Chemoheterotroph
Psychrophiles/Cryophiles
0°C to 20 °C
Mesophiles
20°C to 45 °C
Thermophiles
50°C to 60 °C
Requires oxygen for growth
Obligate aerobes
Can grow either with or without oxygen
Facultative anaerobes
Cannot grow in the presence of oxygen
Obligate anaerobes
Can survive in the presence of oxygen but
do not use oxygen for metabolism
Aerotolerant anaerobes
Requires a reduced level of oxygen for growth
Microaerophiles
do not require high salt concentration but
grows in 2% to 15% salt concentration.
Facultative halophiles
Requires extra carbon dioxide (5% to 10%)
Capnophiles
requires high salt concentrations or hypertonic environments (30% salt).
Obligate halophiles
little or no cell division; intense metabolic
activity
Lag Phase
AKA “Exponential growth phase”; cell
begins to divide; active cellular
reproduction with constant minimum
generation time; cells are at their most
active state
Log (Logarithmic) Phase
Time required for one cell to divide into two
cells
Generation Time (Doubling time)
the density (cloudiness or turbidity) of
bacterial culture in log phase can be
correlated to CFU/ml of the culture.
Method used in AST.
Density measurement
used to estimate the number of bacteria.
Direct counting under the microscope
growth rate slows down (# of new cells = #
of microbial deaths = population stabilizes)
period of equilibrium
Stationary Phase
growing dilution of colony-forming units per
milliliter(CFU/ml)
Direct plate count
logarithmic decline; number of deaths
exceeds the number of new cells formed
Death Phase
used the phenotypic markers for the identification of bacteria
Metabolic differences
Two mechanisms of Carbohydrate utilization
Fermentation and Respiration
obligate aerobes and facultative anaerobes
➢ Aerobic process of energy production
➢ ATP-generating process; glucose is
completely broken down
Respiration (oxidation)
➢ Anaerobic process of energy generation
➢ The end products are mixtures of lactate,
butyrate, ethanol, and acetoin
Fermentation
➢ Major pathway in conversion of glucose to
pyruvate
➢ Anaerobic; does not require oxygen
➢ Used by many bacteria, including
members of Enterobacteriaceae
➢ End-product: 2 molecules of pyruvic acid
Embden-Meyerhof-Parnas (EMP Glycolytic
Pathway)
➢ Used by heterolactic fermenting bacteria
like Lactobacilli and Brucella abortus, which lacks some of the enzymes required in EMP pathway.
➢ Provides pentoses for nucleotide synthesis
➢ While it does involve oxidation of glucose,
its primary role is anabolic rather than
catabolic.
Pentose Phosphate pathway
➢ Converts glucose-6-phosphate (rather than
glucose) to pyruvate and glyceraldehyde
phosphate
➢ Aerobic process used by Pseudomonas,
Alcaligenes, Enterococcus faecalis, and other bacteria lacking certain glycolytic enzyme
➢ End-product: glyceraldhyde-3-phosphate
and pyruvic acid
Entner-Doudoroff pathway
Aerobic Pathways
Aerobic Utilization of Pyruvate (oxidation)
allowing complete oxidation of pyruvate
Krebs Cycle (TCA Cycle)
generate energy in the form of ATP *This cycle results in the production of acid and the evolution of carbon dioxide.
Electron Transport Chain
eukaryote: cytoplasm
prokaryote: cytoplasm
Glycolysis
eukaryote: mitochondrial matrix
prokaryote: cytoplasm
Krebs Cycle
eukaryote: mitochondrial inner membrane
prokaryote: plasma membrane
ETC
This results to results to acid production resulting to color change
Sugar Fermentation
➢ Determine the ability of an organism to use
sodium citrate, malonate or acetate as the
sole source of carbon
➢ Indicator: Bromthymol blue
Citrate, Malonate, or Acetate Utilization
➢ Determines the end products of glucose
fermentation
➢ First pathway produces mixed acid (MR
becomes red)
➢ Second pathway produces acetoin (VP
becomes pink-red)
MR-VP (Clark and Lubs medium)
Yeasts → ethanol
Alcohol fermentation
Streptococcus and Lactobacillus → lactic
acid
Homolactic fermentation
Lactobacillus → mixed acids (lactic, formic
and acetic acid; alcohols)
Heterolactic fermentation
Propionibacterium acnes → propionic acid
Propionic acid fermentation
Escherichia, Salmonella, and Shigella →
mixed acids (lactic, acetic, succinic and
formic acids)
Mixed acid fermentation
Klebsiella, Enterobacter, and Serratia →
acetoin and 2,3-butanediol
Butanediol fermentation
Clostridium spp., Fusobacterium, and Eubacterium → butyric acid, acetic acid, etc.
Butyric acid fermentation
A pairs with?
T
___ pairs with C
G
A DNA sequence that carry hereditary information that encodes for a specific product (peptide/ RNA)
Gene
Duplication of chromosomal DNA for
insertion into a daughter cell
Replication
all genes taken together within an organism. (e.g. 103 – 106 )
➢ i. Chromosome
➢ ii. Extrachromosomal elements
Genome
Contains all genes essential for growth and replication
Chromosome
encodes products that are determinants of
antimicrobial resistance
Plasmids
simplest mobile piece of DNA
IS (insertion sequence)
mobile elements that contain additional
genes
Transposons
is the synthesis of single stranded RNA (w/
the aid of the enzyme RNA polymerase)
using one strand of the DNA as the
template
Transcription
code consists of triplets of nucleotide bases.
Codons
triplet of bases on the tRNA that bind the triplet of bases on the mRNA. It identifies w/c amino acid will be in a specific location in the protein
Anticodon
➢ synthesis of specific protein
➢ conversion of mRNA sequence into amino acids
➢ the number and sequence of amino acids
in a polypeptide & thus the character of particular protein are determined by sequence of codons in the mRNA molecule.
Translation
Method by which genes are transferred or exchanged between homologous regions on 2 DNA molecules
Genetic Recombination
Insertion or deletion of one or more
nucleotide pairs.
Frameshift mutation
Change in the original nucleotide sequence of a gene or genes.
Mutations
Change in one base
Base Substitution (Point mutation)
Two courses of Transduction
Lytic Cycle and Lysogenic Cycle
Uptake and incorporation of naked DNA
into a bacterial cell
Transformation
able to take up free DNA.
➢ H. influenzae
➢ S. pneumoniae
➢ N. gonorrhoeae
Competent
phage DNA incorp. to bact. genes; phage DNA expressed in site; lysis ensues at later time
Lysogenic Cycle
Transfer of bacterial genes by a
bacteriophage
Transduction
replication of bact. chrom. disrupted; phage particles formed; cell lysed and phage
released
Lytic Cycle
➢ Mobilization of donor bacterium’s Plasmid
➢ Plasmid is replicated
Plasmid Transfer
➢ Due to cell-to-cell contact- sex pilus
➢ Mobilization of donor bacterium’s
chromosome
➢ Both plasmids and chromosomal genes can be transferred by this method
Conjugation: Donor to recipient strain
produced by bacteria to cut incoming foreign DNA to prevent incorporation into their genome
Restriction Enzymes
be incorporated into chromosome of
plasmids. “Jumping genes”
Transposon Transfer
