Final Flashcards
1
Q
Sterilization
A
Removal or destruction of all forms of microbial life
2
Q
Commercial sterilization
A
A process that uses heat to destroy microorganisms and spores in food, making it safe to eat and extending its shelf life
3
Q
Disinfection
A
Control directed at destroying harmful microorganisms
4
Q
Antisepsis
A
Disinfection applied to living tissue
5
Q
Degerming
A
The process of reducing the number of microorganisms on living tissue or skin. It’s usually done by mechanical means, such as scrubbing or wiping
6
Q
Sanitization
A
Lowering microbial counts to safe public health levels
(Not considered sterile, skin protective barrier)
7
Q
Bacteriostasis
A
Does not kill but stops or inhibits further growth
8
Q
Asepsis
A
Absence of significant contamination (bacteria)
9
Q
Biocide or Germicide
A
terms used to describe substances that kill or inhibit the growth of living organisms
‘cide’ to kill
10
Q
Microbial death
A
Death usually occurs at a constant rate
11
Q
Microbial control agents
A
Alteration of membrane permeability
Damage to proteins and nucleic acids
12
Q
Alteration of membrane permeability
A
Its the change in the ability of a cell’s membrane to control what enters and exits the cell
Alteration causes ‘leaky’ cells, loss of cellular contents
13
Q
Damage to proteins and nucleic acids
A
Damage causes the loss of replication and metabolic function
14
Q
Microbial Control-Physical Methods
A
- Heat
- Filtration
- Low temperature
- High pressure
- Dessication
- Osmotic pressure
- Radiation
15
Q
What factors need to be taken into consideration for any control method
A
- Population size
- Population composition
- Concentration of agent
- Duration of exposure
- Local environment
16
Q
Microbial Control - Heat
A
Heat kills primarily through enzyme denaturation
Thermal Death Point (TDP)
Thermal Death Time (TDT)
Decimal Reduction Time (DRT)
17
Q
Thermal Death Point (TDP)
A
Lowest temperature at which all microorganisms in a liquid culture are killed, usually in 10 minutes
If TDP for a bacteria is 80°C, it means heating the culture to 80°C for 10 minutes will kill all the bacteria
18
Q
Thermal Death Time (TDT)
A
The shortest time needed to kill all microorganisms in a specific substance (like food or a liquid) at a specific temperature.
It helps measure the effectiveness of heat sterilization.
19
Q
Decimal Reduction Time (DRT)
A
D-value, is the minimum time it takes to kill 90% of microorganisms at a given temperature
20
Q
Moist heat
A
Kills microorganisms through the coagulation of proteins
Moist heat is more effective than dry heat because water conducts heat better
21
Q
Moist heat - boiling
A
Kills most vegetative bacteria, viruses, and fungi, but may not destroy all spores
22
Q
To have reliable and proper sterilization
A
Higher temperatures need to be achieved by using steam under pressure (Autoclave)
Steam must penetrate all areas of the product
23
Q
Autoclave
A
Uses high pressure free-flowing steam at 1atm (15 psi) at (121°C for 15-20 minutes) to kill all microorganisms, including spores
- Putting steam under pressure brings its temperature higher
- Not everything will come out of the autoclave sterile
- There are rules for what you put in an autoclave so that it can be effective
24
Q
Pasteurization
A
Lowers microbial numbers and eliminates pathogenic microorganisms that can be harmful
25
HTST
High-temperature short-time pasteurization
Milk can be pasteurized in 15 seconds
26
Dry heat sterilization
Flaming: material is heated to a red glow
Hot-air sterilization: items heated in a dry oven (170oC for 2h)
27
Flaming
A quick sterilization technique where the object (e.g., inoculation loop or needle) is passed through a flame and heated to a red glow.
28
Hot-air sterilization
Items are heated in a dry oven (170°C for 2h)
29
Bactericidal
Kills the bacteria directly with heat
30
Microbial Control - Filtration
Used to sterilize heat sensitive materials
0.22μm required for filter sterilization
Like vaccines and antibiotics
31
HEPA
High efficiency particulate air filtration
32
Microbial Control - Low Temperature
Low temps slow down the growth and reproduction of microorganisms
Freezing does not always kill the microorganism, periods of dormancy will vary depending on the species
There is no sterilization, its not guaranteed to kill
33
Refrigeration has a ___ effect
Bacteriostatic effect
34
Bacteriostatic
Prevention of the growth of bacteria
35
High Pressure
High pressure disrupts the structure of microbial cells, damaging proteins, membranes, and DNA.
But endospores are more resistant
36
Desiccation (drying)
Removes water from microbes, which is essential for their survival and metabolism.
Without water, microbes cannot grow or reproduce.
37
Osmotic Pressure
Uses high concentrations of salt or sugar to draw water out of microbial cells (osmosis). This dehydration inhibits growth and reproduction.
Typically used in food preservation
38
Microbial Control - radiation
Involves using energy in the form of electromagnetic waves (like gamma rays, X-rays, or ultraviolet (UV) light) to destroy microorganisms
Sterilizing radiation can be ionizing or nonionizing
39
Ionizing radiation
Gamma rays, X-rays, high energy electron beams
40
Non-ionizing Radiation
Has longer wavelengths (UltraViolet light)
Damages DNA by creating thymine dimers which inhibit replication
41
For surface disinfection what radiation is the most common?
Non-ionizing radiation is the most common
(UV)
42
Microwave Radiation
Has little direct effect on microorganisms
Heat action kills most vegetative cells
43
Microbial Control - Chemical
Used on living tissue and inanimate objects
Doesn't eliminate all M.O, usually lower the amount of microorganisms to safe levels
No single disinfectant will achieve complete sterility under all conditions
Contact time is important!
The longer the exposure, the more likely the chemicals will have time to destroy or deactivate the harmful microorganisms
44
The standard method for testing the effectiveness of disinfectants is
The dilution test
45
A Disinfectant solution is tested with three bacteria
To test a disinfectant solution, it is often tested against different bacteria to assess its effectiveness.
- Salmonella choleraesuis
- Staphylococcus aureus
- Pseudomonas aeruginosa
46
Disk-diffusion method
A test to check how well disinfectant work. A paper disk soaked in the agent is placed on an agar plate with bacteria. The agent spreads out, creating a "zone of inhibition" where bacteria can't grow. A larger zone means the agent is more effective.
47
Therapeutic dose
The amount of a medication that produces the desired effect in treating a specific condition without causing harmful side effects
48
Disinfectant Types
1. Phenol and phenolics
2. Bisphenols
3. Biguanides
4. Halogens
5. Alcohols
6. Heavy metals
7. Surfactants
8. Quaternary Ammonium Compounds
9. Food Preservatives
10. Antibiotics
11. Aldehydes
12. Gaseous chemosterilizers
13. Peroxygens
49
Phenol and phenolics
(disinifectant)
Phenol = carbolic acid; significant antibacterial effect above 1% (really strong, and smells)
Phenolics = derivatives of phenol that injure plasma membrane, its less irritating so its used more in healthcare settings
50
Bisphenols
A type of disinfectant that fights against a wide range of gram positive bacteria
Derivatives of phenol containing two phenolic groups
e.g. hexachlorophene inhibits gram positives
51
Biguanides
Broad-spectrum disinfectants that are particularly effective against Gram-positive bacteria
Biocidal against most vegetative cells
Chlorhexidine is a well-known biguanides used in antiseptic solutions and hand sanitizers.
52
Halogens
Are strong oxidizing agents that destroy the cellular protein, nucleic acid, and cell wall or membrane
e.g. iodine and chlorine
Chlorine is commonly used for water disinfection
53
Alcohols
Kill bacteria and fungi but not endospores
54
Heavy metals
Antimicrobial activity defined as oligodynamic action
Oligodynamic action is the ability of small amounts of certain metals to kill microorganisms
55
Surfactants
Break down oil and dirt (soap)
56
Quaternary Ammonium Compounds
Kill by disrupting microbial cell membranes
57
Food Preservatives
Added to food to help preservation
58
Antibiotics
Kill bacteria or inhibit their growth
59
Aldehydes
Inactivates proteins
60
Gaseous chemosterilizers
Cold sterilization
61
Peroxygens
Can be disruptive
62
Paul Ehrlich
Magic bullet theory
He believed that it was possible to create a drug that could target and destroy harmful microorganisms without harming the human body.
The idea was that a "magic bullet" could specifically seek out and attack a pathogen (like bacteria) while leaving the healthy cells unharmed
Helped with the development of antibiotics
63
Antibiotic
Antibiotics work by targeting specific features of bacterial cells, this allows the antibiotic to harm the bacteria without damaging the host (the person being treated)
64
What are most antibiotics produced with
More than half of antibiotics used are produced by Streptomyces spp.
65
What makes mycobacteria harder to treat compared to other bacteria?
Mycobacteria have mycolic acid in their cell walls, which makes them waxy and difficult to penetrate. This protective barrier makes it harder for antibiotics and other substances to affect the bacteria.
66
Narrow spectrum antimicrobial drugs
Are effective against a specific group of microorganisms
67
Broad spectrum antimicrobial drugs
Work against a wider range of microorganisms, including both Gram-positive and Gram-negative bacteria
They are useful when the exact type of microorganism causing the infection is not known
68
Antibiotic of last resort
Vancomycin (harsh on kidneys)
69
Inhibition of cell wall synthesis
These drugs prevent the formation of the bacterial cell wall, especially the peptidoglycan layer
70
Inhibition of protein synthesis
These drugs interfere with the bacterial ribosomes, which are responsible for making proteins.
Some drugs, like chloramphenicol and tetracyclines, bind to the 50S or 30S ribosomal subunits, blocking protein production
71
Disruption of Plasma Membrane
Antimicrobial drugs damage the bacterial cell membrane, making it more permeable. This leads to leakage of metabolites
72
Inhibition of nucleic acid synthesis
Interfere with DNA replication and transcription
73
Inhibition of essential metabolite synthesis
Some drugs, like sulfanilamide, work by mimicking a substance essential for bacterial growth, such as para-aminobenzoic acid (PABA). This causes competition and inhibits the production of folic acid, which is needed for bacterial metabolism.
73
Penicillins (17%)
Inhibit cell wall synthesis
Produced naturally or semi-synthetically
Prevent cross-linking of peptidoglycans
74
Natural Penicillins
Extracted from cultures of Penicillium
The most common natural penicillin is Penicillin G, which is a narrow-spectrum antibiotic. This means it's most effective against a specific group of bacteria, mainly gram-positive bacteria
75
Semi-synthetic Penicillins
Are modified versions of natural penicillins.
By altering the side chains of the natural penicillin molecule, scientists can make them more effective against a wider range of bacteria.
These modified penicillins have a broader spectrum of activity, meaning they work against both gram-positive and gram-negative bacteria
76
Carbapenems Drug
- Carbapenems inhibit cell wall synthesis in bacteria
- These drugs are effective against a wide variety of bacteria.
- Class of β-lactam antibiotics
- Primaxin is a commonly used carbapenem
77
Monobactams
- Low toxicity
- Single ring structure
- Effect gram-negative bacteria such as pseudomonas and E. coli.
78
β-lactam antibiotics
Means a group of antibiotics that all have a β-lactam ring in their structure. This ring is what makes them effective at killing bacteria by stopping the bacteria from building their cell walls, which they need to survive.
79
Cephalosporins Drug
- Inhibit cell wall structure similarly to penicillin
- Resistant to penicillinases
- Effective against many gram-negative
80
Polypeptide antibiotics
e.g. bacitracin: inhibits cell wall synthesis at an earlier stage
e.g. vancomycin: toxicity a problem – considered last line of defense for multi- drug resistant Staphylococcus aureus
81
Antimycobacterial antibiotics
- Used to treat infections caused by Mycobacterium species, such as tuberculosis
- Isoniazid (INH) is an antimycobacterial antibiotic that works by inhibiting the synthesis of mycolic acids in the bacterial cell wall
82
Chloramphenicol and Aminoglycosides Drug
Are used to treat bacterial infections
Have a broad spectrum but can be toxic to the host
Inhibits protein Synthesis
83
Tetracyclines
- Broad spectrum inhibits protein synthesis
- Produced by Streptomyces spp.
- Penetrate body tissue well so effective against urinary tract infections,
mycoplasmal pneumonia, STDs
84
Macrolides Drug
- Contain macrocyclic lactone ring
e.g. erythromycin – inhibits protein synthesis
- More effective against gram-positive streptococcal and staphylococcal infections
85
Polymyxin B
Effective against gram-negative bacteria
Injures plasma membranes
Traditionally used against infections caused by Pseudomonas
86
Rifamycins
e.g. rifampin
Inhibit mRNA synthesis
Penetrates tissues and reaches therapeutic levels in cerebrospinal fluid and abscesses
87
Quinolones and Fluoroquinolones
Quinolones and Fluoroquinolones
e.g. nalidixic acid (quinolone group):
selectively inhibits DNA gyrase, required in DNA replication
e.g. ciprofloxacin (fluoroquinolone):
widespread use against anthrax
88
Sulfonamides Drug
- Also known as sulfa drugs
- Among first synthetic drugs used to treat microbial disease
- Inhibits synthesis of essential metabolites
- Generally considered to be bacteriostatic
89
Antifungal Drugs
e.g. azole antibiotics
Used against athlete’s foot and vaginal yeast infections
90
Antiviral Drugs
Antiviral Drugs
Many are analogs of nucleosides and nucleotides
e.g. acyclovir used in treatment of most herpesvirus infections
91
Antiprotozoan and Antihelminthic Drugs
e.g. quinine used to control malaria
e.g. niclosamide used to treat tapeworm infections from sushi
92
Drug Resistance
1. Destruction or inactivation of the drug
2. Prevention of target site penetration alteration
3. Alteration of target site
4. Rapid efflux
93
Genome
Genetic information in a cell
94
Genotype
The specific genetic makeup of an organism
95
Phenotype
Observable traits of an organism
96
Bacterial genetics
Bacteria have a single circular chromosome, supercoiled ( DNA gyrase) and attached to the plasma membrane
97
E.coli DNA has __
4.6 million base pairs
98
Genomics
Is the study of genomes and understanding the functions and interactions within the genome
99
Three stages of molecular information flow
1. Replication
2. Transcription
3. Translation
100
Replication
Duplication of DNA
101
Transcription
DNA participating in protein synthesis through RNA
102
Translation
Determination of amino acid sequence
It takes place in the cytoplasm
In prokaryotes translation happens faster
103
Archaea reverse __
Gyrase
104
DNA Replication
Cellular DNA replicates before cell division
Each daughter cell receives identical chromosome to parent cell
DNA is replicated from the 3' end
105
Semiconservative replication
Each new double-stranded DNA molecule contains one original (conserved) strand and one new strand
106
In some bacteria DNA replication is ___
Bidirectional
107
Polymerase Chain Reaction
Method to quickly make many copies of DNA in a lab( vitro)
Uses DNA polymerase to build new DNA strands
Thermocyclers are machines that involve repeatedly heating and cooling the DNA sample
108
Transcription
Synthesis of RNA from DNA
109
Three types of RNA in bacterial cells
messenger RNA, ribosomal RNA and transfer RNA
110
Translation
Sequence of codons on mRNA determines amino acid sequence in the protein being synthesized
In prokaryotes, translation of mRNA into protein can begin even before transcription is complete, as both processes occur in the cytoplasm. Since mRNA is produced directly in the cytoplasm, there is no need for transport, allowing translation to start immediately
111
Sense codons
Code for amino acids
112
Nonsense codons
Stop codons – signal end of protein molecule synthesis
113
What is the start codon in bacteria
AUG
In bacteria start codon (AUG) codes for formylmethione where AUG codes for methionine in other regions of the protein
114
tRNA
Assists in the transport of required amino acids during protein synthesis
115
Start codons are available to ___
Ribosomes
116
Repression
Regulatory mechanism that inhibits gene expression and decreases the synthesis of enzymes
Usually a response to the overabundance of an end-product mediated by repressor proteins
117
Induction
Process that turns on transcription of a gene induced by an inducer
e.g. lactose metabolism in E. coli: the enzymes needed for lactose metabolism are produced only when lactose is present, activating gene expression.
118
Operon model of expression
Explains how a group of genes is regulated and expressed together in prokaryotic cells, particularly in bacteria like E. coli
Operon is a set of operator and promoter sites and structural genes
119
Mutation
Change in the base sequence of DNA.
(simple mutations can be silent and not effect the function)
Silent - you don’t see it expressed
120
Base substitution (point mutation)
single base in DNA sequence is replaced with a different one
121
Missense mutation
A type of base substitution where the change in DNA leads to a different amino acid being added to the protein, potentially altering its function
122
Nonsense mutation
A base substitution creates a stop codon in the middle of the sequence, which results in the premature termination of the protein and a non-functional protein
123
Frameshift mutations
One or a few nucleotide pairs deleted or inserted in the DNA shifting the reading frame
124
Spontaneous mutations
These mutations occur naturally, without any external cause or mutagen. They can happen due to errors in DNA replication or repair
125
Mutagens
Environmental agents that directly or indirectly bring about mutations
126
Chemical mutagens
Nitrous acid
Nucleoside analog
127
Light-repair enzymes
These enzymes repair DNA damage caused by ultraviolet (UV) light.
Photolyases absorb visible light and use that energy to break the bond between the dimers, restoring the DNA to its original state.
128
Dark-repair: nucleotide excision repair
Mechanism that fixes DNA damage
The process involves cutting out the damaged section of DNA and filling in the gap with new, correct nucleotides
Does not need light
129
Mutation rate
The probability that a gene will mutate when a cell divides
130
Identifying Mutants
Detection through the selection of an altered phenotype
131
Positive or direct selection
Method used to identify mutant cells by allowing them to grow while rejecting the unmutated (wild-type) parent cells
132
Negative or indirect selection
Identifies cells that cannot perform a certain function
133
Auxotroph
Any mutant microorganism with a nutritional requirement that is absent in the parent
Anything that requires something to be given to them by the parents (something that the parent didn’t need but they do)
134
Carcinogens
Mutagens that cause cancer in animals or humans
135
Ames test
Uses bacteria as carcinogen indicators, based on back-mutations or reversions
136
Systematics, phylogeny
Study of evolutionary history of organisms
137
Molecular techniques, like ribosomal RNA (rRNA) sequencing, revealed two types of prokaryotes
Bacteria: pathogenic prokaryotes, soil and water nonpathogens, photoautotrophs
Archaea: methanogens, extreme halophiles, hyperthermophiles
138
Bergey’s Manual of Systematic Bacteriology
Is a classification guide for prokaryotes (bacteria and archaea).
- Prokaryotic species refer to a group of cells with similar traits.
- A pure culture is a population of cells from a single parent cell, essentially a clone.
- A strain is a subgroup within a species with slight differences from others.
139
Bergey’s Manual of Determinative Bacteriology helps identify prokaryotes using characteristics like ___
Cell wall composition, shape, staining patterns, oxygen needs, and biochemical tests.
140
Biochemical tests
biochemical tests help identify bacteria by checking for certain enzymes they produce.
Can be examined using selective and differential media
These tests help scientists figure out where bacteria live and what they can do, like if they can survive in the stomach or on food.
141
Serological tests
Method used to identify microorganisms based on their antigenic properties
(structure)
Positive identification based on agglutination reaction
142
Phylum 1 - Proteobacteria
All are gram negative
Metabolically diverse
Many have medical, industrial and agricultural significance
143
α-proteobacteria
Many capable of growth at very low nutrient levels
Include appendaged bacteria
Agriculturally important nitrogen fixing bacteria
Plant and human pathogens
144
Purple phototrophic bacteria
Carry out anoxygenic photosynthesis
Very colorful
Include purple sulfur bacteria and purple non-sulfur bacteria
145
Nitrifying bacteria
Utilize inorganic nitrogen compounds
Nitrification results from two groups of microorganisms (ammonia-oxidizers and nitrite-oxidizers)
i.e. nitrosifyers and nitrifiers
146
Sulfur and Iron-oxidizing bacteria
- Grow on reduced sulfur compounds
- Mostly gram negative
- Two ecological classes: neutral pH and acid pH
e.g. Thiobacillus
147
Hydrogen-oxidizing bacteria
- Use H2 as the sole electron donor and O2 as electron acceptor
- Both Gram-positive and Gram-negative hydrogen bacteria are known
- Contain one or more hydrogenase enzymes
- Grow in microoxygen environments
148
Pseudomonas and the pseudomonads
Straight or slightly curved aerobic rods
Scattered phylogenetically within the proteobacteria
Variety of nutriton sources
Many are pathogenic
149
Acetic acid bacteria
- Gram-negative, aerobic, motile rods
- They incomplete oxidize sugars or alchohol and produce acetic acid end products
- Relatively high tolerance to acidic conditions
- All members of alpha-proteobacteria
150
Free-living aerobic nitrogen-fixing bacteria
- They live primarily in soil
- They need oxygen to survive (aerobic)
- Fix nitrogen on their own
- Members of alpha- or gamma- proteobacteria
151
Enteric bacteria
- Homogeneous group of Gram- negative, nonsporulating rods
- Nonmotile or motile by peritrichous flagella
- Facultatively aerobic (can survive with or without oxygen)
- Many pathogenic strains (some can cause illness)
152
Vibrio and Photobacterium
- They have a fermentative metabolism (form of antibiotic metabolism)
- Most are aquatic (freshwater or marine)
- Some, like Vibrio cholerae, can make people sick
- Photobacteria emit light (luminescence) and contain enzyme luciferase (they can glow in the dark)
153
Rickettsias
- Almost exclusively obligate intracellular parasites (bacteria that can only survive and grow inside the cells of other organisms)
- Can cause significant human pathogens (e.g. Rocky Mountain spotted fever, Q fever)
- Wolbachia are intracellular parasites of arthropod insects
154
Spirilla
- Motile and spiral-shaped
- Some are nitrogen-fixers, others are magnetotactic
- Bdellovibrio prey on other bacteria (bacterial predators)
155
Sheathed proteobacteria
- They belong to the group filamentous betas with a unique life cycle
- Inside the sheath, they create tiny cells with tails (flagellated swarmer cells) that can swim away and start new colonies
- Common in freshwater habitats containing rich organic matter
156
Budding and prosthecate/stalked bacteria
- Organisims that grow extra parts, like: stalks, hyphae or appendages
- These extra parts, called prosthecae, are surrounded by the cell wall
- Exhibit polar growth rather than typical intercalary pattern
157
Gliding Myxobacteria (a final question)
- Specialized form of motility
- Members of delta proteobacteria
- They exhibit the most complex behavioral patterns and life cycles of all known prokaryotes
- Myxococcus is an example
158
Sulfate and sulfur-reducing proteobacteria
- Sulfate and sulfur function as electron acceptors under anoxic conditions
- They aree mostly in aquatic and terrestrial environments that have become anoxic due to microbial decomposition
- Canned foods can get “sulfide stinker” spoilage pattern
159
Phylum 2: Gram-positive bacteria
Divided into two major phylogenetic subdivisions:
high G + C ratio and low G + C ratio
160
G + C base ratio
The G + C base ratio is a way of measuring how much of an organism's DNA is made up of guanine (G) and cytosine (C)
161
Low G + C Gram positive bacteria: sporeformers
- Sporeformers can make endospores
- e.g. Clostridium spp., Bacillus spp.
- They are mostly found in soil
- Clostridial diseases include tetanus (C. tetani), botulism (C. botulinum) and gas gangrene (C.perfringens)
162
Low G + C Gram positive bacteria: staphylococci
- Some of the bacteria do not form spores
e.g. Staphylococcus spp.
- Common parasites of humans and animals – can be found on skin and mucous membranes
- Produce several toxins and enzymes which aid in their pathogenicity (help them cause disease)
163
Low G + C Gram positive bacteria: lactobacilli
- Includes lactic acid bacteria
- Produce lactic acid as a byproduct which inhibits growth of competing organisms (e.g. Lactobacillus)
- Lactobacilli used commercially in food production
- All grow anaerobically (absence of oxygen)
164
Low G + C Gram positive bacteria: streptococci
- Streptococci also produce lactic byproducts
- Responsible for a number of significant human diseases (e.g. S. pyogenes)
- Are grouped based on how they react with blood on an agar plate
165
Low G + C Gram positive bacteria: Listeria and Enterococcus
- Listeria are Gram-positive coccobacilli
- L. monocytogenes is a type of listeria that causes listeriosis – major foodborne illness
- Survives refrigeration temperatures
- Enterococci live in areas of the body with lots of nutrients and are a common cause of infections you can get in hospitals
166
Low G + C Gram positive bacteria: Mycoplasmas
- “wall-less” bacteria (no peptidoglycan)
- Highly pleomorphic (can change shape a lot)
- They can form long, filaments, similar to how fungi grow.
- Smallest self-replicating organisms
167
High G + C Gram positive bacteria: Coryneform bacteria
- Typically rod-shaped but form irregular cell arrangements
- Include animal and plant pathogens
e.g. Corynebacterium diphtheriae
168
High G + C Gram positive bacteria: Propionic acid bacteria
- First discovered in Swiss cheese
- Ferment glucose to propionic acid
e.g. Propionibacterium acnes
169
High G + C Gram positive bacteria: Mycobacterium
- Distinctive cell wall (acid-fast stain) containing mycolic acid
- Separated into slow and fast-growing groups
e.g. Mycobacterium tuberculosis
170
High G + C Gram positive bacteria: Actinomycetes
- Large group of filamentous bacteria
e.g. Streptomyces spp.
- Primarily found in soil
- Characteristic earthy odour (geosmin compounds)
- Antibiotic producers
171
Phylum 3: Cyanobacteria and Prochlorophytes
Cyanobacteria -
- Characteristic blue-green pigmentation
- Carry out oxygenic photosynthesis
- Contain N-fixing cells: heterocyst's
- Possess gas vacuoles and perform gliding motility
Prochlorophytes -
- Oxygenic phototrophs containing chlorophyll a and b
- e.g. Prochloron, Prochlorothrix and Prochlorococcus
172
Domain Archaea
Highly diverse group of prokaryotes - morphologically and physiologically
173
Euryarchaeota
Physiologically diverse group of Archaea
Many inhabit extreme environments
* Examples: high temp, high salt, high acid
174
Haloarchaea
Key genera: Halobacterium, Haloferax, Natronobacterium
Extremely halophilic Archaea
Have a requirement for high salt concentrations
– Typically require at least 1.5M NaCl for growth
Found in artificial saline habitats (e.g., salted foods), solar salt evaporation ponds, and salt lakes
– Reproduce by binary fission
– Do not form resting stages or spores
– Most are nonmotile
– Most are obligate aerobes
– Possess adaptations to life in highly ionic environments
Cell wall is composed of glycoprotein and stabilized by Na+
175
Water balance in extreme halophiles
Halophiles need to maintain osmotic balance
* This is usually achieved by accumulation or synthesis of compatible solutes
Halobacterium species instead pump large amounts of K+ into the cell from the environment
* Intracellular K+ concentration exceeds extracellular Na+ concentration and positive water balance is maintain
