Chapter 4 Flashcards
essential nutrients of microbe
compounds that a microbe must have but cannot make
• Supplied by environment
macronutrients
nutrients needed in large quantities
• Six major elements: C, O, H, N, P, S
• Cations that serve as cofactors for specific enzymes:
Mg2+, Fe2+, K+, Ca2+
micronutrients
• Co, Cu, Mn, Zn, Mo, Ni
•Energy must be stored
• Chemical energy (ATP)
membrane potential
when chemical energy pumps protons outside of the cell
nitrogen gas
its 79% of earths atm, but most organisms can’t use gas form (N2)
the nitrogen cycle requires
nitrogenfixing bacteria to convert N2 to NH4+(ammonium) using nitrogenase enzyme
Selective permeability is achieved in three ways
• Substrate-specific carrier proteins (permeases) in the
membrane
• Nutrient-binding proteins that patrol periplasmic space
• Membrane-spanning protein channels (pores) that
discriminate b/w substrates
passive diffusion
- uncharged molecules, like 02 and co2, cross membrane
* Follows concentration gradient
facilitated diffusion
- Transporters pass material into/out of cell
* Follows concentration gradient
coupled transport
Uses energy released from one molecule transported down gradient to transport a second molecule against its gradient
symport
molecules move in the same direction
antiport
molecules move in the opposite direction
example of group translocation
- phosphotransferase system (PTS)
- Uses (PEP) to attach phosphate to sugars
- Glucose becomes glucose-6-phosphate
Selective media
favor growth of one organism over another
differential media
expose biochemical differences b/w species
Example of medium that is both selective and
differential
• MacConkey lactose medium
-Only gram-negative bacteria grow (selective)
-Only species capable of fermenting lactose produce
pink colonies (differential)
How do we know unculturable microbes exist?
- All known microorganisms have rRNA
- rRNA is highly conserved across the phylogenetic tree
- PCR/sequencing of soil and water compared to known culturable organisms shows undiscovered microbes
growth rate
increase of cell numbers, exponential
• If a cell divides by binary fission, the # of cells = 2^n
generation time
*FOR GROWTH IN PURE CULTURE
Nt = N0 x 2^n (NO original cell #)
• Generation time, g = t/n
growth rate constant
number of generations per unit time (usually per hour)
k = n/t
• Remember generation time g = t/n
• So, k = 1/g
batch culture
• A liquid medium within a closed system. The simplest way to show effects of a changing environment is to culture bacteria
Distinct stages in biofilm development
Initiation, Maturation, Maintenance, Dissolution
• Form thick extracellular matrix (e.g. EPS) – increase
antibiotic resistance of residents within biofilm
spores
• Certain gram-positive bacteria (Clostridium, Bacillus)
can form spores
• Don’t grow and don’t need nutrients until they germinate
heterocysts
Anabaena. fix nitrogen anaerobically while maintaining oxygenic photosynthesis
gliding motility
Myxococcus xanthus uses this – uses pilus to travel
fruiting body
Starvation starts cycle where 100,000+ cells clump to form this.
Myxococci within the fruiting body differentiate into
thick walled spores and are released into surroundings (to find nutrients)
cell cycle
lag log stationary death
