The words you are searching are inside this book. To get more targeted content, please make full-text search by clicking here.
Discover the best professional documents and content resources in AnyFlip Document Base.
Search
Published by shakirahsara0830, 2021-03-17 01:42:26

MICROORGANISM

MICROORGANISM

MICROORGANISM

A microorganism, or microbe, is a microscopic organism, which may 1
exist in its single-celled form or a colony of cells. The possible existence
of unseen microbial life was suspected from ancient times, such as in
Jain scriptures from 6th century BC India.

The possible existence of unseen microbial life was suspected from ancient times, such as

in Jain scriptures from 6th century2 BC India. The scientific study of microorganisms began

with their observation under the microscope in the 1670s by Antonie van Leeuwenhoek. In the

1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory

of spontaneous generation. In the 1880s, Robert Koch discovered that microorganisms caused

the diseases tuberculosis, cholera, diphtheria and anthrax.

Microorganisms include all unicellular organisms and so are extremely diverse. Of the three

domains of life identified by Carl Woese, all of the Archaea and Bacteria are microorganisms.

These were previously grouped in the two domain system as Prokaryotes, the other being the

eukaryotes. The third domain Eukaryota includes all multicellular organisms and many

unicellular protists and protozoans. Some protists are related to animals and some to green

plants. Many of the multicellular organisms are microscopic, namely micro-animals,

some fungi, and some algae, but these are not discussed here.

They live in almost every habitat from the poles to

the equator, deserts, geysers, rocks, and the deep sea. Some are adapted to

extremes such as very hot or very cold conditions, others to high pressure, and a few,

such as Deinococcus radiodurans, to high radiation environments. Microorganisms

also make up the microbiota found in and on all multicellular organisms. There is

evidence that 3.45-billion-year-old Australian rocks once contained microorganisms,

the earliest direct evidence of life on Earth.[1][2]

Microbes are important in human culture and health in many ways, serving to ferment

foods and treat sewage, and to produce fuel, enzymes, and other bioactive

compounds. Microbes are essential tools in biology as model organisms and have

been put to use in biological warfare and bioterrorism. Microbes are a

vital component of fertile soil. In the human body, microorganisms make up

the human microbiota, including the essential gut flora. The pathogens responsible

for many infectious diseases are microbes and as such are the target of hygiene 2
measures.

BACTERIA

Bacteria are single celled microbes. Bacteria are
classified into five groups according to their basic
shapes: spherical (cocci), rod (bacilli), spiral (spirilla),
comma (vibrios) or corkscrew (spirochaetes).They can
exist as single cells, in pairs, chains or clusters.

3

Bacteria like archaea are prokaryotic – unicellular, and having no cell nucleus or other
membrane-bound organelle. Bacteria are microscopic, with a few extremely rare
exceptions, such as Thiomargarita namibiensis.[56] Bacteria function and reproduce as
individual cells, but they can often aggregate in multicellular colonies.[57] Some species
such as myxobacteria can aggregate into complex swarming structures, operating as
multicellular groups as part of their life cycle,[58] or form clusters in bacterial
colonies such as E.coli.
Their genome is usually a circular bacterial chromosome – a single loop of DNA,
although they can also harbor small pieces of DNA called plasmids. These plasmids can
be transferred between cells through bacterial conjugation. Bacteria have an
enclosing cell wall, which provides strength and rigidity to their cells. They reproduce
by binary fission or sometimes by budding, but do not undergo meiotic sexual
reproduction. However, many bacterial species can transfer DNA between individual
cells by a horizontal gene transfer process referred to as
natural transformation.[59] Some species form extraordinarily resilient spores, but for
bacteria this is a mechanism for survival, not reproduction. Under optimal conditions
bacteria can grow extremely rapidly and their numbers can double as quickly as every
20 minutes.[60]

4

ALGAE

Algae are the organisms, often microorganisms, other than
typical land plants, that can carry on photosynthesis. Algae
are sometimes considered as protists with chloroplasts. ...
Green algae are single-celled organisms that form colonies,
or multicellular free-living organisms, all of which have
chlorophyll b.

5

Algae are scarcely populated in soil and their presence in soil and its activities is
smaller when compared to that of either bacteria or fungi. Algal population in soil
usually ranges from 100 to 10,000 numbers per gram of soil. The algae are
autotrophic, aerobic microorganisms and fix CO2 from atmosphere and produce
energy from sunlight and synthesize their own food. The photosynthetic nature of
the algae accounts for their predominance on the surface soils or just below the
surface layer of soil. Algae initiate the accumulation of organic matter on barren
and fretted land, because of their ability to carry out photosynthesis and other
metabolic activities that release polymeric substances. The two major types of
algae present in the soil belong to green algae and diatoms group. Soil algae are
broadly divided into four major classes, i.e., Cyanophyta (blue–green algae),
Chlorophyta (grass-green algae), Xanthophyta (yellow–green algae), and
Bacillariophyta (diatoms). Out of these four classes, class Cyanophyta (blue–green
algae) and Chlorophyta (grass-green algae) are more abundant in soil. Algae of the
class Chlorophyta and Bacillariophyta are dominant in the soils of temperate
region while blue–green algae are dominant in tropical
soils. Chlorella, Chlamydomonas, Chlorococcum are some of the common genera
of green algae (chlorophyta) present in the soil, whereas Navicula, Pinnularia are
some of the genera of diatoms present in the soil. Most of the soil algae,
especially blue–green algae act as cementing agent in binding soil particles and
thereby prevent soil erosion. In uncropped soil, soil algae check the loss of
nitrates through leaching and drainage. They liberate large quantity of oxygen
through photosynthesis in the soil environment and thus facilitate the aeration in
submerged soils. In tropical soils, soil algae maintain soil fertility.

6

A fungus (plural: fungi or funguses) is any member of
the group of eukaryotic organisms that includes
microorganisms such as yeasts and molds, as well as
the more familiar mushrooms. These organisms are
classified as a kingdom, which is separate from the
other eukaryotic life kingdoms of plants and animals.

FUNGI

7

Fungi can be single celled or very complex multicellular organisms. They are found in just about any habitat but most live on the 8

land, mainly in soil or on plant material rather than in sea or fresh water. A group called the decomposers grow in the soil or on

dead plant matter where they play an important role in the cycling of carbon and other elements. Some are parasites of plants

causing diseases such as mildews, rusts, scabs or canker. In crops fungal diseases can lead to significant monetary loss for the

farmer. A very small number of fungi cause diseases in animals. In humans these include skin diseases such as athletes’ foot,

ringworm and thrush.

Types of fungi

Fungi are subdivided on the basis of their life cycles, the presence or structure of their fruiting body and the arrangement of and

type of spores (reproductive or distributional cells) they produce.

The three major groups of fungi are:
•Multicellular filamentous moulds.
•Macroscopic filamentous fungi that form large fruiting bodies. Sometimes the group is referred to as ‘mushrooms’, but the

mushroom is just the part of the fungus we see above ground which is also known as the fruiting body.
•Single celled microscopic yeasts.

PROTOZOA

. Protozoa are single celled organisms. They come in many
different shapes and sizes ranging from an Amoeba which
can change its shape to Paramecium with its fixed shape and
complex structure. They live in a wide variety of moist
habitats including fresh water, marine environments and the
soil

9

Protozoa (also protozoan, plural protozoans) is an informal term for a group of single-celled eukaryotes, either free-living or parasitic,
which feed on organic matter such as other microorganisms or organic tissues and debris.[1][2] Historically, protozoans were regarded
as "one-celled animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as
found in plants and many algae.[3][4] Although the traditional practice of grouping protozoa with animals is no longer considered valid,
the term continues to be used in a loose way to describe single-celled protists (that is, eukaryotes that aren't animals, plants, or fungi)
that feed by heterotrophy.[5] Some examples of protozoa are Amoeba, Paramecium, Euglena and Trypanosoma.
In some systems of biological classification, Protozoa remains a high-level taxonomic group. When first introduced by Georg
Goldfuss in 1818, Protozoa was erected as a class within the animals,[6] and its etymology is literally "first animals". In later
classification schemes it was elevated to a variety of higher ranks, including phylum, subkingdom and kingdom, and sometimes
included within Protoctista or Protista.[7] With the advent of techniques such as molecular phylogenetics, it was realized that Protozoa
did not represent a natural group; but while it is not an accepted taxon in cladistic analyses, some systematists continue to use it as a
formal taxon.[8]In a series of classifications proposed by Thomas Cavalier-Smith and his collaborators since 1981, Protozoa has been
ranked as a kingdom.[9][10][11] The seven-kingdom scheme presented by Ruggiero et al. in 2015, places eight phyla under Kingdom
Protozoa: Euglenozoa, Amoebozoa, Metamonada, Choanozoa sensu Cavalier-
Smith, Loukozoa, Percolozoa, Microsporidia and Sulcozoa.[8] Notably, this kingdom excludes several major groups of organisms
traditionally placed among the protozoa, including the ciliates, dinoflagellates, foraminifera, and the parasitic apicomplexans, all of
which are classified under Kingdom Chromista. Kingdom Protozoa, as defined in this scheme, does not form a natural group or clade,
but a paraphyletic group or evolutionary grade, within which the members of Fungi, Animalia and Chromista are thought to have
evolved.[8]

10

VIRUS

Viruses are acellular microorganisms, which means
they are not composed of cells. Essentially, a virus
consists of proteins and genetic material—either DNA
or RNA, but never both—that are inert outside of a
host organism.

11

Viruses are the smallest of all the microbes. They are said to be so small that 500 million rhinoviruses (which cause the common
cold) could fit on to the head of a pin. They are unique because they are only alive and able to multiply inside the cells of other
living things. The cell they multiply in is called the host cell.
A virus is made up of a core of genetic material, either DNA or RNA, surrounded by a protective coat called a capsid which is made
up of protein. Sometimes the capsid is surrounded by an additional spikey coat called the envelope. Viruses are capable of latching
onto host cells and getting inside them. H3N2 influenza virus particles, coloured transmission electron micrograph (TEM). Each virus
consists of a nucleocapsid (protein coat) that surrounds a core of RNA (ribonucleic acid) genetic material. Surrounding the
nucleocapsid is a lipid envelope that contains the glycoprotein spikes haemagglutinin (H) and neuraminidase (N). These viruses were
part of the Hong Kong Flu pandemic of 1968-1969 that killed approximately one million people worldwide. H3N2 viruses are able to
infect birds and mammals as well as humans. They often cause more severe infections in the young and elderly than other flu
strains and can lead to increases in hospitalisations and deaths.
Viruses only exist to make more viruses. The virus particle attaches to the host cell before penetrating it. The virus then uses the
host cell’s machinery to replicate its own genetic material. Once replication has been completed the virus particles leave the host by
either budding or bursting out of the cell (lysis).

12

PROTOZOA

Prions are virus-like organisms made up of a prion protein. These
elongated fibrils (green) are believed to be aggregations of the protein
that makes up the infectious prion. Prions attack nerve cells producing
neurodegenerative brain disease. "Mad cow" symptoms include glazed
eyes and uncontrollable body tremor.

13

Protozoa are single celled organisms. They come in many different shapes
and sizes ranging from an Amoeba which can change its shape
to Paramecium with its fixed shape and complex structure. They live in a
wide variety of moist habitats including fresh water, marine environments
and the soil.
Some are parasitic, which means they live in other plants and animals
including humans, where they cause disease. Plasmodium, for example,
causes malaria. They are motile and can move by:
•Cilia - tiny hair like structures that cover the outside of the microbe. They
beat in a regular continuous pattern like flexible oars.
•Flagella - long thread-like structures that extend from the cell surface. The
flagella move in a whip-like motion that produces waves that propel the
microbe around.
•Amoeboid movement - the organism moves by sending out pseudopodia,
temporary protrusions that fill with cytoplasm that flows from the body of
the cell.

14

LICHEN

A lichen is a composite organism that emerges from algae or
cyanobacteria living among the filaments (hyphae) of the
fungi in a mutually beneficial symbiotic relationship. The
fungi benefit from the carbohydrates produced by the algae
or cyanobacteria via photosynthesis.

15

In some ways, the symbiotic relationship between lichens and algae
seems like a mutualism (a relationship in which both organisms
benefit). The fungus can obtain photosynthates from the algae or
cyanobacterium and the algae or cyanobacterium can grow in a drier
environment than it could otherwise tolerate. However, most
scientists consider this symbiotic relationship to be a
controlled parasitism (a relationship in which one organism benefits
and the other is harmed) because the photosynthetic organism grows
less well than it would without the fungus. It is important to note
that such symbiotic interactions fall along a continuum between
conflict and cooperation.

Lichens are slow growing and can live for centuries. They have been used in foods and to extract chemicals as dyes or
antimicrobial substances. Some are very sensitive to pollution and have been used as environmental indicators.
Lichens have a body called a thallus, an outer, tightly packed fungal layer called a cortex, and an inner, loosely packed
fungal layer called a medulla (Figure 1). Lichens use hyphal bundles called rhizines to attach to the substrate.

16

SLIME MOLD

Slime mold or slime mould is an informal name given to several
kinds of unrelated eukaryotic organisms that can live freely as
single cells, but can aggregate together to form multicellular
reproductive structures. Slime molds were formerly classified as
fungi but are no longer considered part of that kingdom.

17

The term slime mold embraces a heterogeneous assemblage of organisms
whose juxtaposition reflects a historical confusion between superficial resemblances
and actual relationships. The Myxomycetes (true slime molds) are characterized by a
plasmodial stage and definite fruiting bodies. Other slime molds include Protostelia
(minute, simple slime molds), Acrasia (cellular slime
molds), Plasmodiophorina (parasitic slime molds), and Labyrinthulina (net slime
molds). Slime molds are found worldwide and typically thrive in dark, cool, moist
conditions such as prevail on forest floors. Bacteria, yeast, molds, and fungi provide
the main source of slime mold nutrition, although the Plasmodiophorina feed
parasitically on the roots of cabbage and other mustard-family plants.
The life cycle of the Myxomycetes is, allowing for minor variations, representative of that of slime molds generally. The cycle
begins with a spore that has a diameter of 4 to 15 micrometres (1 micrometre equals 0.001 mm, or 0.000039 inch) and that, in the
presence of water, releases a small mass of cytoplasm called a swarm cell. It is propelled by whiplike appendages (flagella) until it
comes in contact with a surface and puts forth pseudopods (lobes of cellular material) that allow it to creep along. In its creeping
phase it resembles an amoeba and is known as a myxamoeba. Both swarm cells and myxamoebae function as sex cells (gametes),
and the fusion of two such cells constitutes the reproductive act of myxomycetes that begins the next stage of growth, the
plasmodium. As the flagella are permanently retracted, the fertilized cell begins to grow by repeated division of its nuclei. The
plasmodium moves gradually in successive waves, creating a characteristic fan shape. A layer of slime, in some species similar to
saliva or mucus, covers the whole plasmodium. The most remarkable metamorphosis of the slime molds occurs next: the growth
from the shapeless plasmodium to an intricately organized spore case, or sporangium. Droplets form at the cell wall and coalesce
to form a cushion and then a stalk that can grow to be 1.25 cm (0.5 inch) wide and 2.5 cm (1 inch) tall. As the column changes to
purple and then black, the sporangium forms at its tip, filled with the dark spores. The sporangium wall dries and disintegrates,
allowing air currents or a sudden movement to release the spores and begin the cycle again.

18

THE STUDY OF MICROORGANISM

As is the case in many sciences, the study of microorganisms can be divided into
two generalized and sometimes overlapping categories. Whereas basic microbiology
addresses questions regarding the biology of microorganisms, applied microbiology
refers to the use of microorganisms to accomplish specific objectives.

19

BASIC MIKROBIOLOGY

The study of the biology of microorganisms
requires the use of many different procedures
as well as special equipment. The biological

characteristics of microorganisms can be

summarized under the following categories:
morphology, nutrition, physiology, reproduction
and growth, metabolism, pathogenesis,
antigenicity, and genetic properties.

20

MORPHOLOGY

Morphology refers to the size, shape, and arrangement of cells. The observation of
microbial cells requires not only the use of microscopes but also the preparation of the
cells in a manner appropriate for the particular kind of microscopy. During the first
decades of the 20th century, the compound light microscope was the instrument
commonly used in microbiology. Light microscopes have a usual magnification factor of
1000 × and a maximum useful magnification of approximately 2000 ×. Specimens can be
observed either after they have been stained by one of several techniques to highlight
some morphological characteristics or in living, unstained preparations as a “wet mount.”

21

SEVERAL MODIFICATIONS OF LIGHT MICROSCOPY ARE AVAILBLE, SUCH AS:

BRIGHT FIELD

The specimen is usually stained and observed while illuminated; useful for observation of the gross
morphological features of bacteria, fungi, algae, and protozoa.

DARK FIELD

The specimen is suspended in a liquid on a special slide and can be observed in a living condition; useful for
determining motility of microorganisms or some special morphological characteristic such as spiral or coiled
shapes.

FLUORESCENCE

The specimen is stained with a fluorescent dye and then illuminated; objects that take up the fluorescent dye
will “glow.”

PHASE CONTRAST 22

Special condenser lenses allow observation of living cells and differentiation of cellular structures of varying
density.

~THE END~


Click to View FlipBook Version