MICRO Exam 2: Microbial growth and nutrition

What are the two types of metabolic reactions

Catabolism and anabolism

What is catabolism

Breaking down of complex nutrients into building blocks and releases energy

What is anabolism

Building of complex molecules from simpler ones, requires energy

Why are metabolic reactions needed

For cells to grow and replicate

What are helpful microbes

Good ones like; medicine, vitamins, and probiotics

What do optimicrobial compounds/treatments do

Prevent microbes from causing disease, spoiling food, contaminating water. As well as manipulating them to make beneficial products like foods, medicines, vitamins, and probiotics

how is the growth of all life related?

they all require the same core elements to grow but get them in different forms and amounts

what are the building blocks for fundamental organic molecules

proteins, nucleic acids, carbohydrates, and lipids

what does microbial growth mean?

an increase in the number of cells aka replication

how does cell division begin?

mother or parent cell duplicates its chromosomes and other contents and doubles in size, it then divides into 2 daughter cells

how does most bacteria reproduce?

binary fission

how many cells does binary fission begin with?

one cell that divides into 2

what is the process of binary fission

the cell duplicates its DNA and other components and divides into two cells, the daughter cells then become independent when a septum grows between them and they separate

where does budding mainly occur

yeast

how does budding work

small new cell develops on surface of existing cell and separates to form daughter cells (small cell grows off of parent cell)

what are the detailed steps of binary fission?

dividing cells replicate their single bacterial chromosome shortly before division; chromosome is attached to the cell membrane (grows and separates the replicated chromosome); cell temporarily may have 2 (or more) chromosomes (if bacterial cell is replicating quickly); cells may not completely separate (diplo, strepto, staphylo, and other cell morphologies)

what does this image represent?

binary fission in prokaryotes

what material is required when culturing bacteria?

culture media with all nutrients necessary for growth

what circumstances is bacteria cultured under

proper environmental conditions including temperature, pH, aeration, solute concentration/osmolarity (varies for different bacterial species)

what is used to estimate viable bacteria in the original sample

colony count and dilution factor

what are the steps to performing a growth curve?

inoculate sterile liquid media in a flask with small number of bacterial cells from a pure culture → incubate cells at optimal conditions → at evenly spaced time intervals, remove small aliquot of sample and plate cells on solid nutrient media → incubate and count bacterial colonies → assume that all cells in a single colony are derived from a single cell → to determine total number of cells, multiply the number of colonies by the dilution factor

how is countable viable/living bacteria expressed?

Colony Forming Units (CFUs) per ml

what does #1 represent with the logarithm of viable cells

it is increasing

what does #2 represent for the logarithm of viable cells

it is constant or not changing

what does #3 represent with the logarithm of viable cells

what is the lag phase

adjustment to the environment; bacteria do not increase in number, but are still metabolically active and adjusting to new culture conditions, cells increase their contents and prepare to divide

what is the exponential (log) phase

once bacteria have adapted to culture conditions, population growth is exponential or logarithmic (2-4-6-8-16-32 cells… etc) cells dividing at their most rapid rate, cells dividing at a constant rate

what is generation time

doubling time; the time it takes to double the population, bacteria can very from 20 minutes to days, many bacteria that are commonly studied replicate in < 1 hour

what is the stationary phase

as growth increases exponentially, nutrients are used up, metabolic waste products accumulate, growth levels off, cell number stays constant (cells exhibit maximum stress resistance to environmental stressors)

what is the death phase

conditions worsen, number of live cells decreases at a logarithmic rate, cells assume unusual shapes (difficult to identify), cells really decrease, generally best not to use old cultures for staining as results can be misleading - best to use young log phase growth cells as they best represent the natural size, morphology, and Gram stain

what can growth curves help determine

infection and disease, food microbiology, industrial microbiology, water treatment, and genetic engineering

what do plate counts measure

serial dilutions

what do hemocytometers measure

direct microscopic counts

what do spectrophotometers measure

measurement of turbidity

what can using heat cells to remove water help measure?

dry weight

what are plate counts

performance of serial dilutions of a microbial sample and plate on nutrient agar

what is the countable CFU range

30-300

what does it mean if something is viable

alive and able to replicate

what can hemocytometers be used in combination with to distinguish between live and dead cells

trypan blue stains

what is a hemocytometer

a glass microscope slide that has a counting chamber that has a grid of squares and perpendicular lines that holds liquids in a suspension

what does turbidity measure

optical density (OD600); measure amount of light transferred through liquid, microbial cells present will scatter light and reduce amount transferred through solution, FAST

what are some problems with measuring turbidity

can’t tell if cells are alive or dead; size of cells change during growth cycle, other variables like dead cell debris affect reading

what is a polymerase chain reaction

sequencing approach that quantifies bacteria and other microbes in environmental and tissue samples without isolating and culturing them

what is a colony

a group of growth of an original cell

how do colonies form

from a single cells, spore, or from a group of the same microorganisms attached to one another in clumps or chains (usually have a distinctive shape, color, surface, etc)

what is defined media

made from ingredients with KNOWN chemical composition; often used when exact nutritional needs of an organism are known

what is complex media

contains ingredients with UNKNOWN chemical compositions; often used for general cultivation of microbes (including those whose nutritional requirements are not known) as it is rich in nutrients

what is general purpose media

media that supports the growht of mant general (non-fastidous/not picky) microbes; complex media that contains a mixture of ingredients/nutrients that support a wide variety of microbial life (ex. nutrient agar, broth, brain-heart infusion, and trypticase soy agar)

what is enriched media

contains complex organic substances (blood, serum, hemoglobin, or special growth factors) that fastidious (picky) bacteria require for growth

what are some growth factors in enriched media

specific vitamins or amino acids

what is selective media

allows only specific types of microbes to grow; contains one or more agents (dyes, antibiotics, acids, high salt concentrations) that inhibit the growth of unwanted organisms

what is differential media

allows you to distinguish between different types of microorganisms that grow based on their appearance; contains agents like fermentable carbohydrates and pH indicators that cause color changes to show different characteristics of microbes that grow