Microbiology is the study of microscopic organisms like bacteria, fungi, and protists. Key developments included the first observation of microbes by Antonie van Leeuwenhoek in 1676 and their role in disease was established. Microbiology has many subdisciplines including medical microbiology, environmental microbiology, and industrial microbiology. Aquatic microbiology involves the study of microbes that live in water environments like streams, lakes, and oceans and how they differ from terrestrial bacteria.

1. By – Annu Maurya

2.  Microbiology (from Greek µῑκρος, mīkros, "small";
βίος, bios, "life"; and -λογία, -logia) is the study of
microorganisms, which are unicellular or cell-
cluster microscopic organisms. This includes
eukaryotes such as fungi and protists, and
prokaryotes. Viruses, though not strictly classed as
living organisms, are also studied. In short;
microbiology refers to the study of life and
organisms that are too small to be seen with the
naked eye.

3.  Microbiology typically includes the study of the
immune system, or Immunology. Generally,
immune systems interact with pathogenic microbes;
these two disciplines often intersect which is why
many colleges offer a paired degree such as
"Microbiology and Immunology
 Microbiology is a broad term which includes
virology, mycology, parasitology, bacteriology and
other branches. A microbiologist is a specialist in
microbiology

4. 
 The existence of microorganisms was hypothesized
for many centuries before their actual discovery in
the 17th century. In 600 BCE, the ancient Indian
surgeon Susruta held microbes responsible for
several diseases and explained in Sushruta Samhita
that they can be transmitted through contact, air or
water.

5.  Bacteria, and other microorganisms, were first
observed by Antonie van Leeuwenhoek in 1676
using a single-lens microscope of his own design. In
doing so Leeuwenhoek made one of the most
important discoveries in biology and initiated the
scientific fields of bacteriology and microbiology.
The name "bacterium" was introduced much later,
by Ehrenberg in 1828, derived from the Greek
βακτηριον meaning "small stick". While Van
Leeuwenhoek is often cited as the first
microbiologist, the first recorded microbiological
observation, that of the fruiting bodies of molds,
was made earlier in 1665 by Robert Hooke

6.  The field of microbiology can be generally divided
into several subdisciplines
 Microbial physiology: The study of how the
microbial cell functions biochemically. Includes the
study of microbial growth, microbial metabolism
and microbial cell structure.
 Microbial genetics: The study of how genes are
organized and regulated in microbes in relation to
their cellular functions. Closely related to the field
of molecular biology.

7.  Cellular microbiology: A discipline bridging
microbiology and cell biology.
 Medical microbiology: The study of the
pathogenic microbes and the role of microbes
in human illness. Includes the study of
microbial pathogenesis and epidemiology and
is related to the study of disease pathology and
immunology.
 Veterinary microbiology: The study of the role
in microbes in veterinary medicine or animal
taxonomy.

8.  Environmental microbiology: The study of the
function and diversity of microbes in their natural
environments. Includes the study of microbial
ecology, microbially-mediated nutrient cycling,
geomicrobiology, microbial diversity and
bioremediation. Characterisation of key bacterial
habitats such as the rhizosphere and phyllosphere,
soil and groundwater ecosystems, open oceans or
extreme environments (extremophiles).
 Evolutionary microbiology: The study of the
evolution of microbes. Includes the study of
bacterial systematics and taxonomy

9.  Industrial microbiology: The exploitation of
microbes for use in industrial processes. Examples
include industrial fermentation and wastewater
treatment. Closely linked to the biotechnology
industry. This field also includes brewing, an
important application of microbiology.
 Aeromicrobiology: The study of airborne
microorganisms.

10.  Food microbiology: The study of microorganisms
causing food spoilage and foodborne illness. Using
microorganisms to produce foods, for example by
fermentation.
 Pharmaceutical microbiology: the study of
microorganisms causing pharmaceutical
contamination and spoil
 Agricultural microbiology: The study of
agriculturaly important microorganisms

11.  Fishery Microbiology: Fisheries microbiology is
that branch of science which deals with the study of
a vast collection of microscopic, unicellular and
largely undifferentiated life from of microscopic
living organism and their effect on the fish and fish
culture

12.  The bacteria whose proper home is in water and
which can developed optimally only in water.
 Other sources of Bacteria in Water
Besides genuine aquatic bacteria, a number of bacteria
from other habitates are also found.
 Soil: Water in close contact with soil
 Air: A constant rain of bacteria falls from the air on
to surface waters Plants, animals and human
 bacteria living in the sea are different from those in
fresh water and amongst the latter those of the rivers
are different from those in lakes.

13.  Majority of aquatic bacteria are heterophilic, i.e. they
live on organic substances.
 Some are photo and chemoautotrophic needing only
inorganic nutrients.
 Morphologically, most aquatic bacteria are similar to
the basic types of terrestrial bacteria.
 In most water predominant bacteria are gram (-).
 The majority of aquatic bacteria are motile, as a rule by
means of flagella.
 Genuine aquatic bacteria are distinguished by their
ability to utilize very small concentration of nutrients.

14.  Bacteria may live in the water free or growing on
some solid substratum.
 Systematically aquatic bacteria are not a
homogenous group, their representatives are found
in almost all orders of the class of Bacteria.
 There are great biological differences between
inland and marine bacteria.

15. Bacteria in inland waters -There are relationships
between the bacterial flora of inland waters and that
of the soil.
Ground water -Ground water is poor in micro-
organisms and in nutrients. Ground water
from different parts of the world examined
included the microorganisms belonging to the
genera:- Achromobacter, Flavobacterium,
Micrococcus, Nocardia, Cytophaga,
Hypomicrobium, Planctomyces, Gallionella,
Caulobacter, Agrobacterium, Clostridium etc.

16.  Spring Water- Spring water contains more or less
similar type of bacteria as mentioned above. Other
bacteria added are iron containing water contain
iron bacteria (Gallionella ferrugina, Leptothrix
ochrcea etc.), thermal springs contain
thermotolerant and thermophilic species (Sulfolobus
acidocaldarius, Leptothrix thermalis, Thermus
aquaticus etc.)

17.  Streams In streams which are poor in nutrients,
gram negative non sporeing rod shaped
predomonate which include- Psedomonas,
Flavobacterium, Acinetobacter, Moraxella etc. with
increasing eutrophication Bacillus and
Enterobacteria gain importance
 River Depending on the sewage load, rivers carry
more or less numerous sewage bacteria which
include Escherichia coli, Proteus vulgaris,
Salmonella sp, Clostridium, Desulfovibrio
desulfuricans etc.

18.  Lakes-- Non sporing rod shaped bacteria
predominant in the lakes of temperate climate.
Looking through the literature, it can be gathered
that bacteria particularly of the genera
Achromobacter, Flavobacterium, Vibrio,
Brevibacterium, Spirillum, Microccus, Sarcina,
Bacillus, Pseudomonas, Nocardia, Streptomyces and
Cytophaga occur widely in lakes. Majority of
bacteria living in salt lakes are halophilic and
halotolerance forms (Halobacterium and
Halococcus).