if you are designing an experiment involving a photolithotrophic autotroph, in addition to light, which of the following would be most essential to maintaining growth of the organism?
a source of CO2
35 colonies grew in nutrient agar from 1.0ml of sample withdrawn from a solution diluted to 10^-5 in a standard plate count procedure. how many cels were in the original sample?
methanogens are potentially of great importance because...
they produce methane, and methane is an excellent energy source
pseudomonads are a large group of bacteria which can...
spoil refrigerated food because they grow at 4C, cause disease in plants and animals, use a number of different substances for carbon and energy sources, and degrade proteins and lipids
when a young, vigorously growing culture of bacteria is transferred to fresh medium of different composition, the lag phase is usually short of absent
which of the following is a desirable general characteristic of antimicrobial drugs
selective toxicity, broad spectrum of activity, and bactericidal rather than bacteriostatic
the lowest concentration of an antibiotic that prevents growth is
minimal inhibitory concentration (MIC)
which of the following does not effect the concentration of a drug in the body
broad spectrum of activity
which of the following is useful mechanism of action for an antibacterial drug
inhibition of cell wall synthesis, inhibition of protein synthesis, interference with RNA and DNA synthesis
A culture system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called ______ culture system
agents that are static and therefore do not kill infecting microorganisms are not useful as chemotherapeutic agents
the drug of last resort that is generally used in treating infections caused by methicillin resistant staphylococcus aureus is
which of the following affects the size of the clear zone in a disk diffusion test of antimicrobial susceptibility
the initial concentration of the drug, solubility of the drug, the diffusion rate of the drug
in order to determine the minimal lethal concentration (MLC) the culture is first inoculated into a medium containing the drug then subcultured into a medium containing
which of the following can be used to isolate pure cultures of bacteria from mixtures
streak plate, spread plate, pour plate
a wide variety of microorganisms are commercially used to manufacture ______ for human consumption
agar is an excellent gelling agent microbiological media because
it is not degraded by most microorganisms and solid agar remains solid until the temperature is raised to 100C and liquid agar remains liquid if the temperature is lowered to 45C are correct
the movement of molecules across a membrane from an area of higher concentration to an area of lower concentration with the use of a carrier molecule embedded in the membrane is called
which of the following is the major reason why it has been difficult to treat viral infections with chemotherapeutic agents?
viruses use the metabolic machinery of their hosts, which limits many of the potential points of attack
the most selective antibacterial agents are those that interfere with bacterial cell wall synthesis. This is because ...
bacterial cell wall snythesis is easily inhibited whereas animal cell wall synthesis is more resistant to the actions of the drugs
chemotherapeutic agents that are chemically modified natural products of microorganisms are most specifically referred to as...
organisms that ignore oxygen and grow equally well in its presence of absence is called
which of the following is a reason for the occurrence of a lag phase in a bacterial growth curve
cells may be old, the medium may be different, organisms could have been injured and need time to recover
an organism with a temperature growth optimum near 80C and a pH growth optimum between 1.0 and 6.5 is usually referred to as
the total number of viable microorganisms remains constant in stationary phase because
either there is a balance between cell divisions and cell death, or there is a cessation of cell division even though the cells may remain metabolically active
which of the following processes can be used to bring nutrients into a cell against a concentration gradient
members of the genus Rhizobium...
grow symbiotically in root nodules of legumes where they fix nitrogen
which of the followinmg is used by microorganisms to become resistant to a particular drug
enzymatic inactivatino of the drug, exclusion of the drug from the cell, an alternate metabolic pathway that bypasses the drug-sensitive step
which of these methods can be used to determine the number of viable microorganisms in a sample
measuring colony forming units per ml
organisms that are damaged by normal atmospheric levels or oxygen (20%) but require oxygen levels of 2-10% for growth are called
organisms that do not require oxygen for growth but grow better in its presence are called
which of the following can be used to estimate the number of microorganisms in a culture
direct counts of microbial cells, counts of viable cells using colony growth procedures, measurement of microbial biomass
defining features of the halobacteria include
absolute dependence on a high concentration of NaCl for growth
which of the following contribute to the differences between archaea and bacteria
archaea lack muramic acid
the length of the lag phase of growth can vary depending on
the condition of microorganisms, the nature of the growth medium, the temperature
which of the following groups of photosynthetic bacteria are capable of oxygenic photosynthesis