Influence of climate on the distribution of microbial species in soil.

1. NAME – BHAWNA SHARMA
COURSE – B.Sc.(H) MICROBIOLOGY, 2ND YEAR
ROLL NO. – 4503
ASSIGNMENT ON
ENVIRONMENTAL
MICROBIOLOGY
TOPIC – INFLUENCE OF CLIMATE ON
MICROBIAL SPECIES DISTRIBUTION
IN SOIL
SUBMITTED TO – Dr. NIDHI CHANDRA
DEPARTMENT OF MICROBIOLOGY
RAM LAL ANAND COLLEGE
UNIVERSITY OF DELHI

2. INTRODUCTION
• Microbes are central to all life forms and exhibits huge
diversity. One teaspoon of topsoil contains around one
billion individual microscopic cells and around 10,000
different species.
• Soil microbial populations determine key soil functions,
thereby directly affecting the value of land.
• Soil microorganisms performs nutrient cycling,
detoxifying pollutants, the production and absorption
of greenhouse gases such as methane and nitrous
oxides.
• Climate may affect microbial populations in soil with
many potential consequences including loss of soil
carbon, change in soil-borne greenhouse gas levels and
alternation to the important plant-soil feedbacks giving
rise to soil fertility.

3. MICROBES AND CLIMATE
CHANGE
• Bacteria and fungi recycle carbon in soils from living and dead
plants.
• It is the activity of soil microbes that determines whether the
carbon is stored underground or released back into the
atmosphere.
• Different types of microbes are produce and consume major
greenhouse gases.
• More than three times as much carbon is stored in soil than in the
atmosphere.
• Temperature rises are predicted to increase bacterial respiration,
leading to release of CO2 and methane into the atmosphere.

4. HISTORY OF RESEARCHDSDS
H
Soil microorganisms and the impact of climate change on their
distribution and response were mostly ignored because
methodological constraints prevented a detailed exploration. But the
following decades would see an exponential growth in this study
which is aided by revolution in the use of both stable isotope
methods that allow the tracing elements through different
components of the soil system, and molecular and metagenomics
approaches that allow for the identification and changes in
abundance, activity and functional potential of soil microbial
communities. It was found that there are many of the climatic
changes that decides the composition of soil microbial community
that includes elevated CO2, warming, drought and many other
climate change drivers.

5. ELEVATED CO2
• It was found that the proportion of fungi would increase under
elevated CO2 because of increased plant litter production. This
was analysed by using Phospholipid Fatty Acid (PLFA) analysis,
which was the first chemotaxonomic method to assess shifts in
total fungal and bacterial abundance as well as shifts in bacterial
community composition based on lipid biomarkers.
• It was found that under low N conditions, elevated CO2
increased both decomposer and AM (Arbuscular Mycorrhiza)
fungal abundance which was assesed using microscopic counts of
observed hyphae.
• It was also found that increased carbon dioxide amount
increases the aplha-proteobacteria, beta-proteobacteria and
Acidobacteria in soil.

6. GLOBAL WARMING
• Warming increased total microbial abundance but it decrease
total bacterial diversity and reduced the relative abundance of
Actinobacteria but increased Acidobacteria.
• Long term warming in forests stands increased the abundance
of bacterial taxa associated with oligotrophic strategies such as
Acidobacteria and Alphaproteobacteria.
• In other field studies, Acidobacteria as well as
Alphaproteobacteria both increased under global warming.
• Fungal abundance also found under warmed conditions.
• It is not clear whether this abundance is the result of warming
directly or indirectly affecting soil microbial communities through
affecting plant growth.

7. DROUGHT
• It has been recognised that soil moisture is an important
driver of the composition and activity of soil communities
• It was found that although irrigation effects on microbial
communities were small, fungal PLFA was highest in the
dry site with a Meditterranean climate.
• It was also found by PLFA analysis that fungi or fungal-
dominated soils are more resistant to drought than
bacteria and bacteria-dominated soils.
• The bacterial phylum Acidobacteria and the class
Alphaproteobacteria increased in abundance during
drought, while Actinobacteria decreased but rapidly
regained their initial abundance.

8. OTHER CLIMATE CHANGE DRIVERS
• The biomass of fungi, both decomposer as well as AM and
gram-negative bacteria decreased strongly after flooding.
• But it was found that fungi benefitted from increased rainfall in
drought-prone prairie soil.
• The lower susceptibility of gram-positive bacteria to flooding
than that of gram-negative bacteria corresponds with earlier
findings that this group of bacteria is more stress-resistant than
gram-negative bacteria.
• There is a decrease in fungal abundance with higher soil
temperatures under reduced snow cover while it was also
reduced in the reduced snow cover treatment with strongly
fluctuating temperatures.
• Snow addition and spring warming reduced the abundance of
Alphaproteobacteria and Betaproteobacteria in subarctic
peatlands.
• There is a seasonal dynamics of microbial communities in alpine
and tundra systems that found a higher abundance of fungi
during winter than during summer.

9. PREDICTION OF THE EFFECT OF CLIMATE
CHANGE ON SOIL MICROBIAL
COMMUNITIES
• Fungi and gram-positive bacteria broadly represents K
strategists or oligotrophic organisms with slow growth rates,
thick cell walls, and the ability to form spores. These
characteristics have been used to explain the stress-resistance
of these microbial groups, which in the case of climate change
translates in a higher resistance to drought and fluctuating
moisture conditions.
• oligotrophy versus copiotrophy affects microbial response to
long-term drought, it was found that drought decreased
average bacterial rRNA operon copy number, which tends to
correlate with copiotrohic strategies such as high maximum
growth rate and the ability to change growth rates quickly.

10. • High moisture content facilitates dispersal between
metacommunities by connecting soil pores, and it has been
suggested that the movement of soil micro and meso-fauna
can aid in community recovery through dispersal of microbes or
their spores.
• The production of intracellular trehalose seems to play a role in
desiccation tolerance in Escherichia coli and the synthesis of
exopolysaccharides in bacteria and Archaea enables optimum
growth at low temperatures.
• Fungal community response to drought had greater
phylogenetic clustering than the response to nitrogen addition
whereas in bacterial community response is same in both the
disturbances.
• Global warming generally increases rate of heterotrophic soil
respiration , N cycling specially nitrification, mineralization and
denitrification .

11. • Global warming also increases the abundance of microbial C
cycling genes and in particular those responsible for
decomposing labile C compounds and this linked to the
observed greater respiration rates.
• Drought is well known to slow down rates of C and N
transformations but result in a flush of C and N mineralization
after rewetting.
• A rainfall event simulated in two drought-stressed agricultural
fields triggered a peak in soil soluble N concentrations and N2O
emissions which significantly increase in the abundance of
nitrifier and denitrifier genes.
• A rapid increase in transcripts of ammonia monooxygenases
and nitrite oxidoreductase after rewetting of dry-soils, were
linked to the reduction in size of soil ammonium pool. This
alters C and N cycling and microbial community as well which is
related to these cycles.

12. Fig. Framework for
predicting soil
microbial community
response to climate
change and the
consequences for soil
functioning.

13. Table : Types of extreme events and associated
hypothesized microbial response traits

14. CONCLUSION
• Microbial groups and bacterial taxa that are associated with
K-strategist or oligotrophic life-history strategies seem to be
consistently increasing in abundance under drought and
warming, while they decrease with elevated CO2. In contrast
under pulse disturbances such as drought followed by
rewetting, the more copiotrophic or r-strategist groups are
rapidly to regain their abundance.
• Functional genes involved in the C and N cycle can predict
the consequences of changes in microbial community
composition in response to climate change for soil
functioning.

15. REFERENCES
1. Franciska T.de Vries, Robert I. Griffiths , 2018, “ Impacts of
Climate Change on Soil Microbial Communities and Their
Functioning”, School of Earth and Environmental Sciences.
2. The Impact of Climate Change on Soil Biodioversity “Why
Do Soil Microbes Matter?”, UK Centre for Ecology &
Hydrology.

16. THANK YOU