Download MICROBIAL NUTRITION

IN THE NAME OF GOD
Islamic Azad University
Falavarjan Branch
School of Biological Sciences
Department of Microbiology
MICROBIAL NUTRITION
By:
Keivan Beheshti Maal
Metabolism
Metabolism – coordination of different
chemical reactions into specific structures
– energy releasing – catabolic rxn – catabolism
– energy requiring – anabolic rxn – anabolism
We will concentrate on
chemoorganotrophs = organic compounds
for carbon and energy
Nutrition
Nutrition – process in which nutrients
acquired from environment and used
for metabolism and growth
Chemical composition of cytoplasm
70% water
proteins
96% of cell is composed of 6 elements
–
–
–
–
–
Carbon
Hydrogen
Oxygen
Phosphorous
Sulfur
5
Nitrogen
Main reservoir is nitrogen gas (N2)
79% of earth’s atmosphere is N2
Nitrogen is part of the structure of proteins, DNA,
RNA & ATP – these are the primary source of N for
heterotrophs
Some bacteria & algae use inorganic N nutrients
(NO3-, NO2-, or NH3)
Some bacteria can fix N2
Regardless of how N enters the cell, it must be
converted to NH3, the only form that can be combined
with carbon to synthesis amino acids, etc.
6
Oxygen
major component of carbohydrates, lipids and
proteins
plays an important role in structural &
enzymatic functions of cell
component of inorganic salts (sulfates,
phosphates, nitrates) & water
O2 makes up 20% of atmosphere
essential to metabolism of many organisms
7
Hydrogen
major element in all organic compounds &
several inorganic ones (water, salts & gases)
gases are produced & used by microbes
roles of hydrogen
– maintaining pH
– forming H bonds between molecules
– serving as the source of free energy in oxidationreduction reactions of respiration
8
Phosphorous
main inorganic source is phosphate (PO4-3)
derived from phosphoric acid (H3PO4) found in
rocks & oceanic mineral deposits
key component of nucleic acids, essential to
genetics
serves in energy transfers (ATP)
9
Sulfur
widely distributed in environment, rocks,
sediments contain sulfate, sulfides, hydrogen
sulfide gas and sulfur
essential component of some vitamins and the
amino acids: methionine & cysteine
contributes to stability of proteins by forming
disulfide bonds
10
Common Nutrient Requirements
macroelements (macronutrients)
– C, O, H, N, S, P, K, Ca, Mg, and Fe
– ~10
– required in relatively large amounts
micronutrients (trace elements)
– Mn, Zn, Co, Mo, Ni, and Cu
– trace amounts
– often supplied in water or in media
components
Requirements for Carbon,
Hydrogen, and Oxygen
often satisfied together
– carbon source - provides H, O and electrons
autotrophs
– carbon dioxide - sole or principal carbon source
– Electrons from other sources
heterotrophs
– organic molecules
sources
-
carbon
and
energy
Nutritional Types of Microorganisms
Organic nutrient – C and H molecules
– Living matter
– Proteins, carbohydrates, lipids, nucleic
acids
Inorganic nutrient – combination of
atoms other than C and H
– Non-living matter
mixotrophy
– chemical energy source (inorganic)
– inorganic H/e- donor
– organic carbon source
Autotrophs – obtain carbon from inorganic
CO2
– Chemoautotroph:
CO2 = carbon source
Inorganic compounds = energy source
Nitrifiers oxidise ammonia or nitrite to nitrate.
Other bacteria oxidise sulfur, hydrogen gas, etc.
– Photoautotroph:
CO2 = carbon source
Light = energy source
Cyanobacteria, purple and green sulfur bacteria
Heterotroph – require organic compounds
as source of carbon
– Chemoheterotroph:
Organic compounds = carbon
energy source
decomposers and most pathogens
and
– Photoheterotroph:
Organic compounds = carbon source
light = energy source
purple and green non-sulfur bacteria.
based on energy source
– phototrophs use light
– chemotrophs obtain energy
oxidation of chemical compounds
from
based on electron source
– lithotrophs use reduced inorganic
substances
– organotrophs obtain electrons from
organic compounds
Four Basic Groups of
Organisms
Figure 6.1
Requirements for Nitrogen,
Phosphorus, and Sulfur
needed for synthesis of important molecules (e.g.,
amino acids, nucleic acids)
Nitrogen: supplied in numerous ways
– organic molecules
– Ammonia (NH3)
– nitrate via assimilatory nitrate reduction (NO3)
– nitrogen gas via nitrogen fixation (N2)
Heterocysts
Special
cells
filamentous
cyanobacteria - fixing
atmospheric nitrogen
Heterocysts
Anabaena sp.
Sulfur: usually supplied as sulfate via assimilatory
sulfate reduction
– H2S, FeS, SO42– Sulfur granules
Phosphorus: usually supplied as
phosphate
– phosphate - main inorganic source
– Limiting nutrient
– Stockpile in polyphosphate granules
inorganic
Growth Factors
organic compounds
essential cell components (or their
precursors) that the cell cannot synthesize
must be supplied by environment if cell is
to survive and reproduce
industrial production of growth factors by
microorganisms
Classes of growth factors
amino acids
– needed for protein synthesis
purines and pyrimidines
– needed for nucleic acid synthesis
vitamins
– function as enzyme cofactors
Table 5.3
Uptake of Nutrients
by the Cell
Some nutrients
diffusion
enter
Most nutrients enter by:
– facilitated diffusion
– active transport
– group translocation
by
passive
Passive Diffusion
Molecules (solutes) move from region of
higher concentration to one of lower
concentration because of random thermal
agitation
Concentration gradient
No energy used
H2O, O2 and CO2 transport
Osmosis – movement of solvents!!
Facilitated Diffusion
similar to passive diffusion
– movement of molecules is not energy
dependent
– direction of movement is from high
concentration to low concentration
– size of concentration gradient impacts
rate of uptake
carrier saturation effect
•rate of facilitated
diffusion increases
more rapidly and
at a lower
concentration
•diffusion rate
reaches a plateau
when carrier
becomes
saturated
Figure 5.1
note conformational change
of carrier
Figure 5.2
Facilitated diffusion…
differs from passive diffusion
– uses carrier proteins (permeases)
– Undergoes conformation change when bound to
substrate
– Returns to original shape after transport
– specificity
– smaller concentration gradient required for
uptake of molecules
– transports glycerol, sugars, and amino acids
– competition
Active Transport
energy-dependent process
– ATP or proton motive force used
moves molecules against the gradient – “uphill”
concentrates molecules inside cell
involves carrier proteins (permeases)
pumps
– carrier saturation effect is observed
or
ABC transporters
ATP-binding
cassette
transporters
observed in
bacteria,
archaea, and
eucaryotes
Figure 5.5
antiport
symport
Figure 5.6
Group Translocation
molecules are
modified as they
are transported
across the
membrane
energy-dependent
process
PTS systemphosphoenolpyruv
ate: sugar
phosphotransferas
e system
Figure 5.7
Iron Uptake
ferric iron (Fe3+) is very
insoluble so uptake is
difficult
microorganisms use
siderophores to aid
uptake
siderophore
complexes with ferric
ion
complex is then
transported into cell
Figure 5.8
growth factors: organic compounds required in small amounts
• not every growth factor is required by all cells
STUDYING MICROORGANISMS
5 Is – inoculation, incubation, isolation,
inspection and identification
Inoculation:
– Grow
or
culture
from
different
specimens
– Microorganism introduced to nutrient
medium (pl. media)
– Aseptic techniques
Isolation:
– Individual cell separated from other cells –
grows on agar as colony
pure culture
– population of cells arising from a single cell
– 3 major techniques – streak plate; pour
plate; spread plate
CO 5
Fig. 5.11
The Spread Plate and
Streak Plate
mixture of cells spread on an agar surface
- individual cells are well separated from
each other
each cell reproduces to form a separate
colony (visible growth or cluster of
microorganisms)
Streak plate technique
inoculating
loop
Figure 5.8
Spread-plate technique
1. dispense cells onto
medium in petri dish
Figure 5.7
4. spread cells
across surface
2. - 3. sterilize spreader
Laboratory Culturing
Trying to get a pure
culture of a single
organism
Unwanted organisms are
called contaminants – try
to avoid them
– more than one colony type
may indicate contamination
Use solid medium to
isolate bacteria rather
than liquid
– can tell that colonies are
separate
– differentiate based on size,
color and shape
Different Colony Morphology
Aseptic Technique - Broth
Aseptic Technique - Plate
The Pour Plate
sample is diluted several times
diluted samples are mixed with liquid agar
mixture of cells and agar are poured into
sterile culture dishes
Figure 5.9
Culture Media
preparations
support
the
(reproduction) of microorganisms
growth
3 properties – physical state; chemical
composition; functional type
Physical state:
– Liquid, semi-solid or solid
– Liquid - broth
– solid - solidified with agar (1 - 5%)
– Semi-solid – (0.3 - 0.5%) – motility tests
Agar – algal sulfated polysaccharide
– Solid at room temperature
– Melts at 100 °C
– Liquid at 45 – 50 °C
– Solidifies at 42 °C
– Bacteria cannot break down agar – can use
gelatin as nutrient source
Cell cultures, host animals
Chemical
composition:
Synthetic or
Defined Media
all
components
and
their
concentrations
are known
Pure organic and
inorganic
compounds
Complex Media
contain
some
ingredients
of
unknown
composition and/or
concentration
Blood,
extracts,
peptone
meat
yeast,
Rich nutrient source
Functional type:
General purpose media
– Supports
growth
of
microorganisms
– e.g., tryptic soy agar
many
Enriched media
– general purpose media supplemented by
blood or growth factors
– e.g., blood agar
– Fastidious bacteria
Selective media
– favour
the
growth
of
some
microorganisms and inhibit growth of
others
– Dyes, antibiotics, bile salts
– Suppress
organisms
growth
of
Gram-positive
– e.g., MacConkey agar
selects for gram-negative bacteria
Differential media
– distinguish between different groups of
microorganisms based on their biological
characteristics
– Dyes (ph indicators), specific nutrients
– Colony size, colour, media colour changes,
formation of gas bubbles or preciptates
– e.g., Blood agar
haemolytic versus nonhaemolytic bacteria
– e.g., MacConkey agar – lactose + neutral
red
Table 5.7
Incubation –
– Optimal temperature, gaseous conditions –
visible colonies
– Days to weeks
Inspection –
– Macroscopic colony characteristics
– individual species form characteristic colonies
– Microscopic analysis
Figure 5.10a
Colony growth
most rapid at edge of colony
– oxygen and nutrients are more available
at edge
slowest at center of colony
in nature, many microorganisms form
biofilms on surfaces
Identification:
– correlate morphological, physiological,
and genetic traits
– Species or strain