Microbes in The Biological World: Ahmad Masood Department of Botany H.D. Jain College, Ara (V.K.S. University, Ara)

MICROBES IN THE BIOLOGICAL
WORLD
AHMAD MASOOD
Department of Botany
H.D. JAIN COLLEGE, ARA
(V.K.S. University, Ara)
 Microbes are the microscopic organisms.
 Ranging from unicellular to multicellular, even
acellular viruses, virions and prions.
 Widespread in nature.
 Most of them are beneficial, some can cause
harm.
 Microbes are included either in PLANTS or ANIMALS by
early men (no proper knowledge).
 Linnaeus (1758) recognised PLANTAE and ANIMALIA as
the two primary kingdoms.
 TWO KINGDOM CLASSIFICATION.
 Basis- Structural and Functional characters such as
locomotion, response to external stimuli, mode of
nutrition, conductile and contractile systems and the
cell wall.
 18th and 19th Century – exploration of Microorganisms.
 Infusoria (meaning minute aquatic creatures found in
freshwater) formed a group under Animalia; included
motile microscopic forms like multicellular invertebrates
and unicellular protozoa and bacteria.
 Others like microalgae and microfungi – placed under
Plantae alongwith other plants.
 Later on bacteria were transferred to Plant kingdom along
with algae, fungi and other higher plants.
 Animal kingdom included protozoa and other animals.
 Middle of the 19th century saw some remarkable
achievements as the knowledge of microbes gained
momentum - “Golden Era of Microbiology”.
 PROTISTA – a new kingdom formed which included
organisms with relatively simple biological organisation.
 Three kingdom system proposed by Haeckel (1886) on
basis of morphological complexities and tissue system,
division of labour and mode of nutrition.
 Protista with algae, fungi, protozoa, and bacteria
represented the organisms lacking morphological
complexities, tissue system, division of labour and having
diversified mode of nutrition.
 The three Kingdoms – PROTISTA, PLANTAE, and
ANIMALIA.
 Discovery of Electron Microscope by Max Knoll
and Ernst Ruska (1932).
 Details of cellular structure studied.
 Recognition of Prokaryotes and Eukaryotes.
 Protista divided into lower Protists
(bacteria, blue-green algae) and higher Protists
(algae, fungi, and protozoa).
 Four kingdom classification by Copeland (1959)
Monera - Prokaryotic Protists
Protoctista - Eukaryotic Protists
Metaphyta - All other plants
Metazoa - All other animals.
 Distinctive mode of nutrition in fungi and some other
heterogeneity among Protoctista led the formation of
another kingdom – Fungi. .
 Five Kingdoms–Monera, Protista, Plantae, Fungi, and
Animalia.
 Popularly known as Five kingdom classification of R. H.
Whittaker (1969).
 Monera – Bacteria, blue-green algae (prokaryotes)
Protista – Microalgal forms, protozoa, slime moulds
(simple eukaryotes)
Plantae – Multicellular photosynthetic eukaryotes
Fungi – Heterotrophic eukaryotes, predominantly
multicellular
Animalia – Multicellular holozoic eukaryotes.
 Bacteria divided into Archaebacteria and Eubacteria.
 Six Kingdom classification by Grey and Dolittle (1982).
 Six kingdoms placed under two super kingdoms:
 Super Kingdom Prokaryota:
• Archaeobacteria
• Eubacteria
 Super Kingdom Eukaryota:
• Protista
• Fungi
• Plantae
• Animalia
 Protists- divided into Archezoa, Protozoa and Chromista.
 Eight Kingdom classification by Cavalier-Smith (1987) -
taking ultrastructural characteristics as well as rRNA
sequencing.
 Archezoa – primitive eukaryotes, unicellular microbes with
70s ribosomes, lack cell organelles like Golgi complex,
mitochondria, chloroplast and peroxisomes e.g., Giardia.
 Chromista–represented by diatoms, brown algae,
cryptomonads, and oomycetes which have their
chloroplasts within the lumen of rough ER rather than in
the cytoplasmic matrix.
 Kingdoms :
 Eubacteria
 Archaebacteria
 Archezoa
 Protozoa
 Chromista
 Plantae
 Fungi
 Animalia
 Cavalier – Smith later on (by 1998) had reduced the total
number of kingdom from eight to six.
 Kingdom Bacteria is divided into
Eubacteria and Archaebacteria
 Eukaryotes included 5 kingdoms
 Kingdom Protozoa
 Unikonts (heterotrophs)
o Kingdom Animalia
o Kingdom Fungi
 Bikonts (primarily photosynthetic)
o Kingdom Plantae (including red and green algae)
o Kingdom Chromista
 Unikonts descendants of uniciliate forms.
Bikonts descendants of biciliate forms.
Some protozoa are unikonts while others are bikonts.
 According to Cavalier-Smith Eubacteria is the oldest group

of terrestrial organisms still living.
 Younger groups i.e., Archaebacteria and all eukaryotes

named as Neomura.
 The position of microbes remained a matter of
discussion,
 the placement and the division of different microbial
groups formed the basis of all those classification,
 Microbes belong to six of the eight kingdoms.
THANK YOU

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MICROBES IN THE BIOLOGICAL

 According to Cavalier-Smith Eubacteria is the oldest group

 Younger groups i.e., Archaebacteria and all eukaryotes

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