Micro Exam #2 Chapt 6,8,11

Physical requirements for microbial growth

• Temperature

• pH

• osmotic pressure (salt)

Minimum growth temperature

is the lowest temperature at which a microorganism can survive and replicate

optimum growth temperature

is the specific temperature where a microorganism grows and divides at its fastest rate

maximum growth temperature

is the highest temperature at which a microorganism can still grow and divide

Psychrophiles

microbes that thrive in cold

• cause food spoilage

15 C

Mesophiles

moderate temperature loving microbes

Thermophiles

microbes that thrive in hot enviorments

• found in hot springs and organic compost

Ex: Hyperthermophiles

What pH do most bacteria grow at

between pH 6.5 and 7.5

What pH do most molds and yeasts grow at

between pH 5 and 6

Acidophiles

grow in acidic environments

Extreme or obligate halophiles require what kind of enviorment

high osmotic
pressure (high salt)

Facultative halophiles

tolerate high osmotic pressure

Obligate aerobes

require oxygen

Facultative anaerobes

grow via fermentation or
anaerobic respiration when oxygen is not available

Anaerobes

unable to use oxygen and most are
harmed by it

Aerotolerant anaerobes

tolerate but cannot use oxygen

Microaerophiles

require oxygen concentration
lower than air

Chemical requirments

carbon, nitrogen, sulfur,

Culture media

Culture medium

nutrients prepared for microbial growth

Sterile

no living microbes

Inoculum

introduction of microbes into a medium

Culture

microbes growing in or on a culture medium

Chemically defined media

exact chemical composition is known

Complex media

extracts and digests of yeasts, meat, or plants; chemical composition varies batch to batch

• nutrient broth

• nutrient agar

Selective media

– Suppress unwanted microbes and encourage
desired microbes
– Contain inhibitors to suppress growth

Differential media

Allow distinguishing of colonies of different
microbes on the same plate

pure culture

A pure culture contains only one species or strain or colony

streak plate method - used to isolated pure cultures

colony

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)

Bacterial Division

Increase in number of cells, not cell size
• Binary fission*
• Budding*
• Conidiospores (actinomycetes)
• Fragmentation of filaments

Generation time of bacterial cultures

Time required for a cell to divide
– 20 minutes to 24 hours
• Binary fission doubles the number of cells each
generation
• Total number of cells = 2number of generations

phases of bacterial growth (growth curve)

Lag phase
• Log phase
• Stationary phase
– Bacteria approach the carrying capacity
• Death phase

Direct Measurement of Microbial
Growth (Plate growth)

Count colonies on plates that have 30 to 300 colonies
(CFUs)
• To ensure the right number of colonies, the original
inoculum must be diluted via serial dilution
• Counts are performed on bacteria mixed into a dish
with agar (pour plate method) or spread on the
surface of a plate (spread plate method)

Direct Measurement of Microbial
Growth (filtration)

Solution passed through a filter that collects bacteria
• Filter is transferred to a Petri dish and grows as
colonies on the surface

Direct Measurement of Microbial
Growth (Direct Microscopic Count)

Volume of a bacterial suspension placed on a slide
• Average number of bacteria per viewing field is
calculated
• Uses a special Petroff-Hausser cell counterNumber of cells counted
Number of bacteria/ml = Volume of area counted

Estimating Bacterial Numbers by Indirect Methods

Turbidity—measurement of cloudiness with a
spectrophotometer
• Metabolic activity—amount of metabolic product is
proportional to the number of bacteria
• Dry weight—bacteria are filtered, dried, and weighed;
used for filamentous organisms

Turbidity

measurement of cloudiness with a spectrophotometer

function of genes

segments of DNA that encode functional products usually proteins

structure and function of Genotype

the genetic makeup of an organism

represents potential properties

structure and function of phenotype

refers to the actual expressed properties of the genes

Replication of microbial genetics

transcription of microbial genetics

translation of microbial genetics

Mutation

change in the genetic material

frameshift m

UV light as mutagen

microbial Genetic recombination

is the process by which microorganisms—primarily bacteria—exchange or incorporate foreign genetic material into their own genomes, creating new genetic combinations and diversity without traditional sexual reproduction

Transformation , conjugation, transduction

microbial genetics Transformation

microbial genetics Conjugation

microbial genetics Transduction

microbial genetics Plasmids

*Brucella spp.

Gram staining :negative

Disease : Undulant fever

*Rickettsia ricketsii

Gram staining :negative

Disease : Rocky Mtn. spotted fever

*Neisseria gonorrhoeae

Gram staining :negative

Disease : Gonorrhea

pair of 2 bacteria bean shape

*Neisseria meningitidis

Gram staining :negative

Disease : Meningococcal meningitis

pair of 2 bacteria bean shape

*Bordetella pertussis

Gram staining :negative

Disease : Whooping cough

*Pseudomonas aeruginosa

Gram staining :negative

Disease : Wound & urinary tract infections

*Legionella pneumophilia

Gram staining :negative

Disease : Legionnaire’s disease

found in streams, pipes, in showers

*Vibrio cholerae

Gram staining :negative

Disease : Cholera

found in salty water

*Escherichia coli O157:H7

Gram staining :negative

Disease : Diarrhea

*Borrelia burgdorferi

Gram staining :negative

Disease : Lyme disease

*Klebsiella pneumoniae

Gram staining :negative

Disease :

Proteus vulgaris

Gram staining :negative

Disease : Urinary tract infections, wound
infections

*Salmonella typhi

Gram staining :negative

Disease : Typhoid fever

Shigella dysenteriae

Gram staining :negative

Disease : Dysentery (bleeding diarrhea)

*Yersinia pestis

Gram staining :negative

Disease : Plague, Black Death

Haemophilus influenzae

Gram staining :negative

Disease : Meningitis (children)

*Helicobacter pylori

Gram staining :negative

Disease :Ulcers/Stomach cancer

*Chlamydia trachomatis

Gram staining :negative

Disease : Conjunctivitis, Trachoma

*Treponema pallidum

Gram staining : negative

Disease : Syphilis

Clostridium botulinum

Gram staining :positive

Disease : Botulism

Clostridium tetani

Gram staining :positive

Disease : Tetanus, Lockjaw

Clostridium perfringens

Gram staining :positive

Disease : Gas Gangrene

Clostridium difficile (C.dif)

Gram staining :positive

Disease : Diarrhea

Listeria monocytogenes

Gram staining :positive

Disease : Listeriosis

Bacillus anthracis

Gram staining :positive

Disease : Anthrax

Staphylococcus aureus

Gram staining :positive

Disease : Endocarditis, Meningitis, MRSA

Streptococcus pyogenes

Gram staining :positive

Disease : Pericarditis

Mycobacterium leprae

Gram staining : positive

Disease : Leprosy

Mycoplasma pneumoniae

Gram staining : positive

Disease : Pneumonia

Corynebacterium diphtheriae

Gram staining :positive

Disease : Diphtheria

Mycobacterium tuberculosis

Gram staining :positive

Disease : Tuberculosis

BSL-1

no special precautions, basic teaching labs

BSL- 2

lab coat, gloves, eye protection

BSL- 3

biosaftey cabnitet to prevent airbron transmission

BSL- 4

sealed, negative pressure; “hot zone”
▪ Exhaust air is filtered twice through HEPA filters

enrichment culture

encourages the growth of the desired microbe by increasing very small numbers of a desired organism’ to detectable levels

• usually a liquid

Genome

the genetic information in a cell

genomics

sequenceing and molecular characterization of genomes

central dogma

Describes how DNA is transcribed to messenger RNA, which is then translated into proteins

dna→rna→protein