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Diversidad microbiana Métodos moleculares y
computancionales aplicados a sistemática y
evolución Osvaldo Delgado PROIMI-CONICET odelgado
_at_proimi.org.ar
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Microbial Diversity Interactions of genetic and
environment
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Traditionally we have seen biodiversity
relative to our own scale of size. Our species
is one of the largest of some 12,500,000 that
now exist and many others that have existed in
the past.
These species have evolved over a period of
about 3,800,000,000 years. During most of this
time only microbial life forms existed. Of the 3
domains of life 2 are exclusively prokaryotic,
but they contain only about 5000 known species.
Many more microbial species are known among the
eukaryotes, but still much fewer than the number
of species of animals and plants.
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Much of biodiversity is not seen by us and was
unknown before the invention of the microscope
by Van Leeuwenhoek in the 17th century. Based
on tradition, all living things were divided into
the plant and animal kingdoms and when microbes
became known, they were placed within this
system bacteria, fungi and algae as plants and
protozoa as animals. Changes became necessary to
accommodate such fundamental differences as
eukaryotic and prokaryotic cells.
Solid, dissolved in insoluble wasts Toxicity and
reclacitrant problems
Macro-organisms evolved from microbes and were
able to extend life to the dry terrestrial
regions of Earth, creating new habitats for
microbes in the process. This was relatively
recent in evolution.
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Relatively little of the existing microbial
diversity is known to man. This means there is a
huge potential to find new resources for
biotechnology. Let us take a brief look at some
of the microbial groups that are known to exist.
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The diversity of living organisms is so great
that there is no single species definition
applicable to all groups. This makes it
impossible to make a meaningful comparison of
diversity between different groups.
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Taxonomic definitions of species In
microbiology - especially bacteria and yeasts
genetically isolated groups of highly similar
organisms (criteria are fertile offspring from
mating, as in the biological species, or more
than 70 genome similarity based on in vitro
quantitative nDNA/nDNA hybridizations, or high
similarity in base sequences of certain
homologous DNA regions). The biological species
- mostly developed by zoologists Dobzhansky
1937 "species are systems of populations the
gene exchange between these systems is limited
or prevented by a reproductive isolating
mechanism or perhaps by a combination of several
such mechanisms." The phylogenetic species - A
monophyletic group composed of the smallest
diagnosable cluster of individual organisms
within which there is a parental pattern of
ancestry and descent.(Cracraft, 1983).
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Estimates of the number of described species and
possible undescribed species of microorganisms.
(World Conservation Monitoring Center, 1992,
Global Biodiversity, D. L. Hawksworth and R. R.
Colwell) Group Described
Estimated Known
Species Species Algae
40,000 350,000
11.0 Bacteria 4,000
3,000,000 0.1 (including
uncultivable) Fungi 70,000
1,500,000 5.0 Protozoa 40,000
100,000 40.0 Viruses
5,000 500,000 1.0
(including plasmids, phages etc.) Total
159,000 5,450,000 3.0
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• Evolutionary Chronometers
• Cellular macromolecules which help to measure
  evolutionary changes
• Universally distributed
• Functionally homologous
• Proper alignment of the sequences
• Slow rate of changes
• Sequences from
• Cytochromes
• Ferredoxins
• Other proteins (ATPases, RecA)
• RNAs

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• Ribosomal RNAs as evolutionary chronometers
• Ancient molecules
• Functionally constant
• Universally distributed
• Moderately well conserved in sequences
• Large number of available sequences

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The true extent of microbial diversity was only
recognized during the past few decades with
development of molecular genetic methods.
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• Molecular fingerprinting
• ARDRA
• RFLP by PFGE
• RAPD
• ITS
• t-DNA
• rDNA sequencing
• Plasmid profile
• SSCP

• Community fingerprinting
• FISH
• DGGE
• T-RFLP
• Real time PCR