Environmental Microbiology
DR. ALAM KHAN
PH.D. MICROBIOLOGY
ASSISTANT PROFESSOR DEPARTMENT OF LIFE SCIENCES
ENVIRONMENT
Environment
The sum total of all surroundings of a living
organism, including natural forces and other
living things, which provide conditions for
development and growth as well as of danger and
damage.
Microbiology
HISTORY
What happened in the 1970s to cause this new field of microbiology to
develop?
Several events occurred simultaneously that highlighted the need for a better
understanding of environmental microorganisms.
The first of these events was the emergence of a series of new waterborne and
food-borne pathogens that posed a threat to both human and animal health.
In the same time frame it became increasingly apparent that, as a result of past
waste disposal practices, both surface water and groundwater supplies are
frequently contaminated with organic and inorganic chemicals.
The simultaneous impact of these events caused scientists to question the notion
that our food and water supplies are safe and also allowed the development of
tools to increase our ability to detect and identify microbes and their activities in
the environment.
Thus, over a relatively short period, the new field of environmental
microbiology has been established.
The initial scientific focus of the field of environmental
microbiology was on water quality and the fate of
pathogens in the environment in the context of protection
of public health.
The roots for water quality go back to the turn of the
twentieth century, when the treatment of water supplies by
filtration and disinfection resulted in a dramatic decrease in
the incidence of typhoid fever and cholera.
Application of these processes throughout the developed
world has essentially eliminated waterborne bacterial
disease except when treatment failures occur.
DIFFERENT ASPECTS
Environmental factors that influence microbial growth are temperature,
oxygen requirements and pH and water availability.
The right temperature, pH and moisture levels vary from one organism
to another.
Microorganisms that grow optimally below 20 °C are called
psychrophiles.
Those with temperatures optima in the range of 20 °C to 50 °C are
mesophiles,
while those that grow best at temperatures higher than 50 °C are
thermophiles.
Hyperthermophiles have an optimum growth temperature between 70 °C
and 110 °C and these are usually members of the Archaea.
Cells that require O2 for growth and metabolism are
obligate aerobes;
obligate anaerobes cannot multiply in the presence of
O2
while facultative anaerobes grow best if O2
is present, but can also grow without it.
Microaerophiles require small amounts of O2
aerotolerant anaerobes (obligate fermenter) are
indifferent to O2.
Each bacterial species can survive within a range
of pH values, but within this range it has a pH
optimum.
Neutrophiles multiply in the range of pH 5 to 8,
acidophiles grow optimally at a pH below 5.5
and alkalophiles above 8.5.
Finally, all microorganisms require water for growth.
Growth of any microorganisms depends not only on a suitable physical
environment, but also on available source of chemicals to use as
nutrients.
All cells contain the macromolecules as follows:
carbohydrates, lipids, proteins, nucleotides. Nucleotides as monomers
are needed for DNA and RNA synthesis and they play important role in
cellular energetics.
Elements that make up cell constituents are called macronutrients or
major elements (C, O, H, N, S, P, K, and Mg).
Trace elements are also essential to microbial nutrition.
The most widely needed trace elements are Fe, Zn and Mn.
The elements needed under specific growth condition are Cu, Co, Mo,
Ca, Na, Cl, Ni and Se. Some bacteria, especially methanogens
Microorganisms derive energy either from sunlight or by metabolising chemical
compounds.
Prokaryotes can live in many environmental habitats because they are able to use
diverse sources of energy and carbon.
Photoautotrophs use the energy of sunlight and CO2 in the atmosphere to synthesize
organic compounds required by many other organisms.
Cyanobacteria are important photoautotrophs that inhabit fresh and saltwater
habitats.
Chemoautotrophs or chemolithotrophs use inorganic compounds (H2, NH3, NO2‒,
Fe2+, and H2S) for energy and derive their carbon from CO2
.Photoheterotrophs use the energy of sunlight and derive their carbon from organic
compounds.
Chemoheterotrophs or chemoorganotrophs use organic compounds for energy and
as a carbon source.
THE FOUR LAWS OF ECOLOGY: THE CLEAREST
EXPLANATION OF WHAT ECOLOGY REALLY MEANS
1) The First Law of Ecology: Everything Is Connected to
Everything Else.
2) The Second Law of Ecology: Everything Must go
Somewhere
3) The Third Law of Ecology: Nature Knows Best
4) The Fourth Law of Ecology: There Is No Such Thing as
a Free Lunch
ATMOECOSPHERE
The atmosphere consists of 78%, Nitrogen; 21%, Oxygen; 0.034%,
carbon dioxide and trace amount of other gases. It is saturated with
water vapour to varying degrees and it may contain droplets of liquid
water, crystals of ice and particles of dust.
Even though the atmosphere is a hostile environment for
microorganisms,
there are substantial number of them in the lower troposphere, because
of thermal gradients. There is rapid mixing.
Many microorganisms growing in the hydrosphere or lithosphere can
become airborne.
Methods of sampling organism in the atmosphere include viable plate
count and direct count method.
Cladosporium is a major fungal constituent of the atmosphere followed
by Puccinia graminis.
