Transcript microorganism

ENVIRONMENT
&
MICROORGANISMS
Doç.Dr.Hrisi BAHAR
MICROORGANISMS
The word microorganism is used to describe
an organism that is so small that can not be
seen without the use of a microscope.
Viruses, bacteria, fungi, protozoa and some
algae are all included in this category.
 Microorganisms are responsible for many of the
changes observed in organic and inorganic
matter (e.g., fermentation and the carbon,
nitrogen and sulfur cycles that occurred in
nature).
Microorganisms in our lives
► Microorganisms as Disease Agents
► Microorganisms and Agriculture
► Microorganisms and the Food Industry
► Microorganisms, Energy, and the Environment
► Microorganisms and the Future
Microorganisms in our lives
 They generate at least half the oxygen we
breathe.
 They are roots of life's family tree. An
understanding of their genomes will help
us understand how more complex
genomes developed.
Microorganisms (microbes)
 Microbiology is the study of microorganisms also
known as microbes.
Microbes are single-celled microorganisms that can
perform the basic functions of life: metabolism,
reproduction, and adaptation.
Except viruses. Viruses can’t metabolize nutrients,
can’t produce and excrete wastes, can’t move
around on their own, or even can’t reproduce unless
they are inside another organism’s cells.
Medical microbiology
 Medical microbiology is both a branch of
medicine and microbiology which deals with
the study of microorganisms including
bacteria, viruses, fungi and parasites which
are of medical importance and are capable
of causing infectious diseases in human
beings.
Mıcroorganisms
Microorganisms are similar to more complex
organisms in that they need a variety of
materials from their environment to function
and accomplish two primary goals .
1-To supply enough energy to manage their
processes
2-To extract building blocks to repair
themselves or procreate.
Environmental factors
affecting the growth of
microorganisms
Mıcroorganisms have
 Physical Requirements
 Chemical Requirements
from the environment where they live.
Physical Requirements
1. Temperature: Microbes are loosely
classified into several groups based on their
preferred temperature ranges.
Physical Requirements
-Temperature A-Psychrophiles: “Cold-loving”. Can grow at 0oC.
Two groups:
 True Psychrophiles: Sensitive to temperatures over
20oC. Optimum growth at 15oC or below.
Found in very cold environments (North pole, ocean
depths). Seldom cause disease or food spoilage.
 Psychrotrophs: Optimum growth at 20 to 30oC.
Responsible for most low temperature food spoilage.
Physical Requirements
- Temperature B. Mesophiles: “Middle loving”. Most bacteria.
 Include most pathogens and common
spoilage organisms.
 Best growth between 25 to 40oC.
 Optimum temperature commonly 37oC.
 Many have adapted to live in the bodies of
animals.
Physical Requirements
- Temperature C- Thermophiles: “Heat loving”.
 Optimum growth between 50 to 60oC.
 Many cannot grow below 45oC.
 Adapted to live in sunlit soil, compost piles, and hot
springs.
 Some thermophiles form extremely heat resistant
endospores.
 Extreme Thermophiles (Hyperthermophiles):
Optimum growth at 80oC or higher. Archaebacteria.
Most live in volcanic and ocean vents.
Physical Requirements
- pH  Most bacteria prefer neutral pH (6.5-7.5).
 Molds and yeast grow in wider pH range, but
prefer pH between 5 and 6.
 Acidity inhibits most microbial growth and is used
frequently for food preservation (e.g.: pickling).
 Alkalinity inhibits microbial growth, but not
commonly used for food preservation.
 Acidic products of bacterial metabolism interfere
with growth. Buffers can be used to stabilize pH.
Physical Requirements
- pH Organisms can be classified as:
A. Acidophiles: “Acid loving”.
 Grow at very low pH (0.1 to 5.4)
 Lactobacillus produces lactic acid, tolerates mild
acidity.
B. Neutrophiles:
 Grow at pH 5.4 to 8.5.
 Includes most human pathogens.
C. Alkaliphiles: “Alkali loving”.
 Grow at alkaline or high pH (7 to 12 or higher)
 Vibrio cholerae and Alkaligenes faecalis
optimal pH 9.
 Soil bacterium Agrobacterium grows at pH 12.
Physical Requirements
- Osmotic pressure Cells are 80 to 90% water.
A. Hypertonic solutions: High osmotic pressure removes
water from cell, causing shrinkage of cell membrane
(plasmolysis).
Used to control spoilage and microbial growth.
 Sugar in jelly.
 Salt on meat.
B. Hypotonic solutions: Low osmotic pressure causes water
to enter the cell. In most cases cell wall prevents excessive
entry of water. Microbe may lyse or burst if cell wall is
weak.
Physical Requirements
- Osmotic pressure Halophiles: Require moderate to large salt
concentrations. Ocean water contains 3.5% salt.
 Most bacteria in oceans.
 Extreme or Obligate Halophiles: Require very high salt
concentrations (20 to 30%).
 Bacteria in Dead Sea
 Facultative Halophiles: Do not require high salt
concentrations for growth, but tolerate 2% salt or
more.
Chemical Requirements
-CarbonMakes up 50% of dry weight of cell.
 Structural backbone of all organic compounds.
 Chemoheterotrophs: Obtain carbon from
their energy source: lipids, proteins, and
carbohydrates.
 Chemoautotrophs and Photoautotrophs:
Obtain carbon from carbon dioxide.
Chemical Requirements
- Nitrogen, Sulfur, and Phosphorus ►
Nitrogen: Makes up 14% of dry cell weight. Used to
form amino acids, DNA, and RNA.
►
Sulfur: Used to form proteins and some vitamins
(thiamin and biotin).
►
Phosphorus: Used to form DNA, RNA, ATP, and
phospholipids.
Chemical Requirements
- Other Elements & Trace Elements Other Elements
Potassium, magnesium, and calcium are often required as
enzyme cofactors. Calcium is required for cell wall
synthesis in Gram positive bacteria
Trace Elements
Many are used as enzyme cofactors.
Commonly found in tap water.
 Iron
 Copper
 Molybdenum
 Zinc
Chemical Requirements
-OxygenOrganisms that use molecular oxygen (O2),
produce more energy from nutrients than
anaerobes.
Microorganisms can be classified based on their
oxygen requirements:
A.Obligate Aerobes: Require oxygen to live.
Disadvantage: Oxygen dissolves poorly in water.
Example: Pseudomonas, common nosocomial
pathogen.
Chemical Requirements
-OxygenB. Facultative Anaerobes: Can use oxygen, but
can grow in its absence. Have complex set of
enzymes.
Examples: E. coli, Staphylococcus, yeasts, and
many intestinal bacteria.
C. Obligate Anaerobes: Cannot use oxygen and
are harmed by the presence of toxic forms of
oxygen.
Examples: Clostridium bacteria that cause
tetanus and botulism.
Chemical Requirements
-OxygenD. Aerotolerant Anaerobes: Can’t use oxygen, but
tolerate its presence. Can break down toxic forms
of oxygen.
Example: Lactobacillus carries out fermentation
regardless of oxygen presence.
E. Microaerophiles: Require oxygen, but at low
concentrations. Sensitive to toxic forms of oxygen.
Example: Campylobacter
Toxic Forms of Oxygen
1. Singlet Oxygen: Extremely reactive form of
oxygen, present in phagocytic cells.
2. Superoxide Free Radicals (O2-.): Extremely toxic
and reactive form of oxygen. All organisms
growing in atmospheric oxygen must produce an
enzyme superoxide dismutase (SOD), to get rid
of them. SOD is made by aerobes, facultative
anaerobes, and aerotolerant anaerobes, but not
by anaerobes or microaerophiles.
Reaction:
SOD
O2-. + O2-. + 2H+ -----> H2O2 + O2
Superoxide
free radicals
Hydrogen
peroxide
Chemical Requirements
-Hydrogen PeroxideHydrogen Peroxide (H2O2): Peroxide ion is toxic and the
active ingredient of several antimicrobials (e.g.: benzoyl
peroxide). There are two different enzymes that break
down hydrogen peroxide:
A. Catalase: Breaks hydrogen peroxide into water and O2.
Common. Produced by humans, as well as many bacteria.
B. Peroxidase: Converts hydrogen peroxide into water
Chemical Requirements
-Hydrogen PeroxideCatalase
2 H2O2----------> 2H2O + O2
Hydrogen
peroxide
Gas
Bubbles
Peroxidase
H2O2 + 2H+----------> H2O
Hydrogen
peroxide
Microbial Stress Response
 A changing environment creates conditions
that can be stressful for microorganisms.
 Microbes have physiological acclimation
mechanisms to survive and remain active in
the face of stress.
 They have to appropriately respond to
numerous adverse conditions in order to
proliferate or at least survive
Stress response in pathogens
 Human pathogens infecting humans respond to
stress situations encountered during transition
from natural environment to the host.
1-Temperature stress
The first signal to an invading bacteria on entry into
the host is an increase in temperature from that of
the environment to the physiological temperature
of the human body (37°C).
Response: * Induction of virulence genes
* Induction of heat shock genes
http://www.ias.ac.in/jarch/jbiosci/21/149-160.pdf
Stress response in pathogens
2-Oxygen stress
The expression of adherence and invasion factors
of several pathogenic bacteria is
regulated by oxygen concentration.
High oxygen usually represses whereas low
oxygen induces invasiveness
Response:Induction and repression of some
genes .
One regulatory network is the Fnr (fumeratenitrate reductase)-dependent control in response
to anaerobiosis
Stress response in pathogens
3-Osmotic stress
 For a pathogenic bacterium which passes from
environmental waters to the human
body for infection, osmolarity is an important criterion to
distinguish between the external and host associated
environments.
 Osmolarity of an aqueous environment is thought to be no
greater than that equivalent to 0·06 M NaCl while in the
intestinal lumen the osmolarity is much higher (equivalent to
0·3 M NaCl) and in the blood stream the bacteria encounters
an osmolarity equivalent to about 0·15 M NaCl.
 Response. Increase in osmolarity is associated with
expression of virulence factors in many pathogenic
organisms.
Stress response in pathogens
4-Metal ion stress
Iron is an essential element for bacterial growth
and many pathogenic bacteria
have evolved highly efficient iron scavenging
systems which are regulated in response to the
iron status of the environment.
 Response: Ex: Low iron concentration leads to
the increased synthesis of virulence
determinants in several pathogenic bacteria.
Stress response in pathogens
5-Presence of Antibiotic as a stress for bacteria
 An untreated microbe maintained under optimal
growth conditions will not be stressed.
*Similarly, the same cell when exposed to an
antibiotic to which it is fully resistant will also not
be stressed.
*When exposed to a lethal concentration of an
antibiotic to which it is susceptible, the cell will be
highly stressed in its quest to survive.
Response:Antibiotic resistance
Stress response in pathogens
ACTIVE
DRUG
ACTIVE
DRUG
Days
Minutes
GROWTH
INHIBITION
(CELL DIVISION)
STRESS RESPONSE
Bacterial response to
environment
 Rapid response crucial for survival
– Simultaneous transcription and translation
– Coordinate regulation in operons and regulons
– Global genetic control through modulons
 Bacteria respond to
–
–
–
–
–
Change from aerobic to anaerobic
Presence/absence of glucose
Amount of nutrients in general
Presence of specific nutrients
Population size
Quorum Sensing
 Bacteria monitor their own population size
– Pathogenesis: do not produce important molecules too
soon to tip off the immune system.
– Light production: a few bacteria make feeble glow, but
ATP cost per cell remains high.
– Bacteria form spores when in high numbers, avoid
competition between each other.
 System requirements
– A signaling molecule that increases in concentration as
the population increases; LMW
– A receptor; activation of a set of genes
Quorum Sensing
 New peptide communication factor enabling
bacteria to 'talk to each other' discovered
http://phys.org/news112885276.html
Chemotaxis and other taxes
 Movement in response to environmental
stimulus
–
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–
–
–
Positive chemotaxis, attraction towards nutrients
Negative: away from harmful chemicals
Aerotaxis: motility in response to oxygen
Phototaxis: motility to certain wavelengths of light
Magnetotaxis: response to magnetic fields
 Taxis is movement
– Includes swimming through liquid using flagella
– Swarming over surfaces with flagella
– Gliding motility, requiring a surface to move over
Starvation Responses
 Bacteria frequently on the bord of starvation
– Rapid utilization of nutrients by community keeps
nutrient supply low
– Normal life typical of stationary phase
– Bacteria monitor nutritional status and adjust through
global genetic mechanisms
 Types of responses
– Lower metabolic rates, smaller size .
– Release of extracellular enzymes, scavenging
molecules
– Production of resting cells, spores.
Microganisms leaving a stressful environment