EXTINCTION OF MICROBES... SHOULD WE CARE? Marilen M. Parungao-Balolong, MSc, SMic Associate Professor Bioweek 2012 BIOSeminar Wednesday, August 15, 2012
EXTINCTION OF MICROBES... SHOULD WE CARE?
Marilen M. Parungao-Balolong, MSc, SMicAssociate Professor
Bioweek 2012 BIOSeminar
Wednesday, August 15, 2012
WE ALWAYS CARED ABOUT PLANT EXTINCTION
Wednesday, August 15, 2012
WE ALWAYS CARED ABOUT ANIMAL EXTINCTION
Wednesday, August 15, 2012
WE ALWAYS CARED ABOUT HUMAN EXTINCTION
Wednesday, August 15, 2012
BUT...MICROBES? ALWAYS TAGGED AS
THE REASON FOR EXTINCTION...
Wednesday, August 15, 2012
MICROBES: THREAT TO PLANTS
Phytophthora infestans = Europe and Ireland, (1840)
Hemileia vastatrix or coffee rust Ceylon (1860s)
Cratocyctis ulmi = Dutch Elm Disease (1900s)
Wednesday, August 15, 2012
MICROBES: THREAT TO HUMANS
BLACK DEATH & SPANISH FLU
Wednesday, August 15, 2012
MICROBES: THREAT TO ANIMALS
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CAN MICROBES FACE EXTINCTION?
Wednesday, August 15, 2012
“Extinction is a Principle of Evolution”
Wednesday, August 15, 2012
EXTINCTION
• Over 99% of the species that have ever lived have become extinct
• Guesstimate: we lose about 1 species per day
• CURRENTLY: they say that we are living in a period of mass extinction (6th) = brought about by human activity as driving force
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“Microbes are Everywhere”
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Wednesday, August 15, 2012
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ca. 4 to 5 × 1030 prokaryotic cells on Earth, with the open ocean, soil, and oceanic and terrestrial
subsurface showing the highest abundances
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A typical coastal water sample contains 107 viruses, 106 bacteria and
103 protists /ml
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Microbes come in diverse forms; however, it is not known how many different species of microbes inhabit the planet....WHY?
Wednesday, August 15, 2012
Microbes come in diverse forms; however, it is not known how many different species of microbes inhabit the planet....WHY?
• problems involved in defining a microbial species
Wednesday, August 15, 2012
Microbes come in diverse forms; however, it is not known how many different species of microbes inhabit the planet....WHY?
• problems involved in defining a microbial species
• majority of prokaryotic cells cannot be easily grown in culture, which is a prerequisite for species identification of microbes
Wednesday, August 15, 2012
Microbes come in diverse forms; however, it is not known how many different species of microbes inhabit the planet....WHY?
• problems involved in defining a microbial species
• majority of prokaryotic cells cannot be easily grown in culture, which is a prerequisite for species identification of microbes
• NOTE: Only about 5000 to 6000 prokaryotic species have been formally described
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With the birth of NON-CULTURE METHODOLOGIES....
Wednesday, August 15, 2012
With the birth of NON-CULTURE METHODOLOGIES....
• At least 1800 species and 1.2 million new genes were found using a shotgun sequencing approach of microorganisms from a single sample in the Sargasso Sea (Venter et al. 2004)
Wednesday, August 15, 2012
With the birth of NON-CULTURE METHODOLOGIES....
• At least 1800 species and 1.2 million new genes were found using a shotgun sequencing approach of microorganisms from a single sample in the Sargasso Sea (Venter et al. 2004)
• About 643 new species were identified using a 99% similarity as delineation between prokaryotic phylotypes or species based on 16S rRNA gene sequences (Venter et al. 2004)
Wednesday, August 15, 2012
With the birth of NON-CULTURE METHODOLOGIES....
• At least 1800 species and 1.2 million new genes were found using a shotgun sequencing approach of microorganisms from a single sample in the Sargasso Sea (Venter et al. 2004)
• About 643 new species were identified using a 99% similarity as delineation between prokaryotic phylotypes or species based on 16S rRNA gene sequences (Venter et al. 2004)
• Up to 7000 viral types have been detected using a metagenomics (community genomics) approach and it is believed that viruses represent the largest unknown sequence space (Breitbart et al. 2002)
Wednesday, August 15, 2012
PROKARYOTIC MICROBES AS SHAKERS & MOVERS OF THE
BIOSPHERE
Wednesday, August 15, 2012
PROKARYOTIC MICROBES AS SHAKERS & MOVERS OF THE
BIOSPHERE
• They invented photosynthesis long before eukaryotes evolved
Wednesday, August 15, 2012
PROKARYOTIC MICROBES AS SHAKERS & MOVERS OF THE
BIOSPHERE
• They invented photosynthesis long before eukaryotes evolved
• Their oxygen production changed the atmosphere to the oxygenic status we are currently experiencing
Wednesday, August 15, 2012
PROKARYOTIC MICROBES AS SHAKERS & MOVERS OF THE
BIOSPHERE
• They invented photosynthesis long before eukaryotes evolved
• Their oxygen production changed the atmosphere to the oxygenic status we are currently experiencing
• Microorganisms degrade and remineralize organic material, others produce methane, reduce sulfate to sulfide, integrate molecular nitrogen or change the forms of inorganic nitrogen
Wednesday, August 15, 2012
PROKARYOTIC MICROBES AS SHAKERS & MOVERS OF THE
BIOSPHERE
• They invented photosynthesis long before eukaryotes evolved
• Their oxygen production changed the atmosphere to the oxygenic status we are currently experiencing
• Microorganisms degrade and remineralize organic material, others produce methane, reduce sulfate to sulfide, integrate molecular nitrogen or change the forms of inorganic nitrogen
• Microorganisms drive the global cycles of carbon, nitrogen, phosphorus and sulfur
Wednesday, August 15, 2012
“WITHOUT MICROORGANISMS
ALL OTHER LIFE FORMS WILL NOT
SURVIVE”
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SO HOW DO THEY ADAPT...
• Symbiosis
• between multicellular organisms with microorganisms showed great evolutionary success (e.g. Lichens = 1500 species)
Wednesday, August 15, 2012
SO HOW DO THEY ADAPT...
• Symbiosis
• between plant roots and fungi (mycorrhiza) = reason for spread of plants in the continents
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SO HOW DO THEY ADAPT...
• Symbiosis
• between coral host and photosynthetic dinoflagellate
• coral host obtains sugars from the algae and the interference of algae with carbon cycling enhances calcification
• reason why coral reefs one of most diverse ecosystem
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SO HOW DO THEY ADAPT...
• Exchange of Genes (Horizontal Gene Transfer or Microbial Sex)
Wednesday, August 15, 2012
SO HOW DO THEY ADAPT...
• Exchange of Genes (Horizontal Gene Transfer or Microbial Sex)
Wednesday, August 15, 2012
CONSEQUENCES OF GENE TRANSFERS
• Cohan (2001)
• gene transfer among species increases diversity
• gene exchange can help to sustain co-existence of genetically different ecotypes
• gene exchange would help protect ecotypes from extinction if the adaptive mutation can be transferred
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BIOGEOGRAPHY OF MICROBES
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ON DISTRIBUTION• Finlay & Fenchel 1999
• “there are no distributional barriers for small free-living organisms such as microbes”
• Finlay et al. 1996
• “global species diversity is inversely related to body size”
• suggests that the shear number of protists makes global dispersal very likely by mechanisms such as hurricanes, ocean circulations, groundwater connections, damp fur, etc
Wednesday, August 15, 2012
ON EXTINCTION
• Cohan, 2001
• “the large number of microbial cells per species makes extinction unlikely, extinction is not a threat”
• works only for “free-living microbes”
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ON ENDEMICITY
• More evidence of endemicity and biogeography is available for microorganisms associated with plants or animals
• Hosts can be considered as islands, which permit the development of endemism in prokaryotes
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EVIDENCE OF EXTINCTION
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EVIDENCES
• Local extinctions (or strong reductions in the abundance of microbial species) probably occur quite frequently, e.g. due to clearing of forests, agricultural activity or erupting volcanoes
• a multicellular organism is best regarded as an association of species — a mini-ecosystem — and many of these species exist only in this association (e.g. coral reefs destruction, microbes in Dodo or mammoth etc)
Wednesday, August 15, 2012
MICROBIAL FOSSILS?
Wednesday, August 15, 2012
ARE THERE FOSSILS TO GUIDE US?
• Listgarten & Loomer 2003
• Detection of microbial fossils is difficult compared to detection of plant and animal fossils
• one of the reasons for our lack of knowledge on extinction rates of microbes.
• Stromatolites (microbial reefs) were globally distributed in the Proterozoic but the abundance decreased markedly and at present there are only a few sites left
• suggests at least local extinctions in the geological past
Wednesday, August 15, 2012
ENDANGERED
• Most free-living microbes are likely not endangered, although their local distribution might vary considerably and local extinctions
• However, associated species may be ‘threatened’ in the same way as the multicellular hosts organisms
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THE INFECTIOUS PARTICLE...
• Emiliani 1982, 1993
• Microbes may also become extinct when one partner in a predator – prey or parasite – host system loses the adaptation race
• Example: As long as the virus cannot find an alternative host, this means self-extinction
Wednesday, August 15, 2012
SO...SHOULD WE CARE ABOUT THE POTENTIAL LOSES
OF MICROBIAL SPECIES???
Wednesday, August 15, 2012
RECALL...the prokaryotic DNA world constitutes a
‘global superorganism’ that shares the gene pool by
horizontal gene transfer, the microbial ‘kamasutra’
(Doolittle 1999)
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Wednesday, August 15, 2012
WITHOUT THEM...CHANGES IN BIOGEOCHEMICAL
CYCLING
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WITHOUT THEM...CORAL BLEACHING
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YOUR CONTRIBUTION
TO THEIR EXTINCTION
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OUR CONTRIBUTIONS TO POSSIBLE EXTINCTION
• antimicrobials
• habitat fragmentation
• pollution and contamination of aquatic systems
• The BIGGER THREAT: Climate Change
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EXTINCTION OF MICROBES... WE SHOULD CARE!!!
Wednesday, August 15, 2012
THANK YOU VERY MUCH!!!
Wednesday, August 15, 2012