The document summarizes a presentation on microbial ecology given by MD Robel Ahmed. It discusses key concepts in microbial ecology including resource allocation trade-offs, ethylene signaling in plants, and pleiotropic effects of genes. It then outlines experiments conducted to study the effects of bacteria and cadmium stress on the ethylene levels and growth of Arabidopsis thaliana plants. The results showed that bacteria containing ACC deaminase, which reduces plant ethylene, increased plant growth under no stress but decreased stress tolerance, while an ACC deaminase deficient mutant had the opposite effects. The findings highlight ethylene's role in balancing growth and stress tolerance.

1. A
PRESENTATION ON
MICROBIAL ECOLOGY
Presented by
MD ROBEL AHMED
STUDENT ID:
L20192E020101
1ST YEAR 1ST SEMESTER
(Master’s)
FACULTY OF LIFE SCIENCE
AND MECICINE
Presented to
XIUFANG HU
PROFESSOR ,
FACULTY OF LIFE SCIENCE AND
MEDICINE
ZHEJIANG SCI-TECH UNIVERSITY
DATE OF SUBMISSION: 30th OCTOBER 2019

2. Some Terminology Related To Topics
Trade-off
 Losing one thing for gaining another.
 Complementary in evolution.

3. Resource Allocation
Planning
Budget
Expense
Implement
location
Time
Delay
PersonnelProject

4. Ethylene
 Important Phyto-hormone.
 Produced via breakdown of methionine.
Properties:
 Limited solubility in 𝐻2 𝑜.
 Never accumulates in cells.
 Rates of production determines effectiveness.
 Abundant in dividing cells and darkness
Functions:
 Row fruit ripening
 Stress tolerance etc.

5. Pleiotropic Effect
The single gene controlling or influencing
multiple (and possibly unrelated)
phenotypic traits.
 Mutation in this type of gene will simultaneously
affect more than one trait.
 Diverse effect of a single gene or gene pair on
several organ system.

6. Abstract
Microorganisms
Mutation
۩ Genetics of resource allocation is well established still today.
۩ But how micro-organism regulate plant life still unclear.
Our assumptions is,

7. Alteration of resource level
like Hormone, Nutrient, and
Environment condition by
various mutations or
microbial effect
Change of
Phenotypic
Expression
Alteration of
Stress Tolerance
Level
Overall effect
on Plants
growth and
development
Abstract

8.  Balancing resource is critical for fitness.
 Ethylene key hormone controlling balance between resource and stress.
Introduction
Up regulate
ethylene
hormone level
Trigger various
physiological
adaptations
Costly to implement.
Effect on growth rate.
Optimal homeostasis is required for proper phenotype and fitness.
Plant

9.  Following traits can be interrupted by mutations or micro-organisms like,
• Generate a novel phenotype.
• Flowering
• Plant germination
• Biomass production
 Alteration of plant phenotype is beneficial or deleterious.
• Physiological adaptation.
• Cope with stress.
Introduction

10. Mechanism of How microorganism impose effect on plant via ethylene signaling?
Micro-
organisms
Auxin Producing
ACC Deaminase Producing
1-aminocyclopropane-1-carboxylic acid (ACC) = Ethylene precursor
Introduction

11. Important Key Points:
 Plant growth and stress tolerance are negatively co-related.
 Growth and stress controlling by Ethylene.
 Increase Ethylene = More stress resistant
 Decrease Ethylene = Investment into growth but reduce stress resistant. (Tradeoff)
Plant Growth ᾳ
𝟏
𝑺𝒕𝒓𝒆𝒔𝒔 𝒕𝒐𝒍𝒆𝒓𝒂𝒏𝒄𝒆
Introduction

12. Materials and Methods
Effect of microbial alteration of ethylene along with Cadmium stress gradient.
Cadmium is a heavy metal widespread in soil.
At low concentration impose,
 Oxidative stress
 Photosynthetic crisis
 yield declines in plants.
 Act as model abiotic stressor.

13. Plant Materials:
 Most widespread and common model plant Arabidopsis thaliana (L).
Wild type referred as (Col-o).
 Ethylene overproducer mutant eto1
 Ethylene insensitive mutant ein3eill
 Plant seeds
Materials and Methods
Col-0
Eto-1 ein3eill

14. Materials and Methods
Bacterial Strains:
 Wild type strain of Pseudomonas putida UW4.
 Isogenic ACC deaminase-deficient mutant (𝐀𝐜𝐝𝐒−)
Pseudomonas putida UW4 is a bacterial species produces ACC deaminase
which is responsible for breakdown of ACC ( ethylene precursor in plants.)

15.  ACC deaminase-deficiency mutant (𝑨𝒄𝒅𝑺−) of Pseudomonas putida UW4.
How we can make 𝑨𝒄𝒅𝑺− mutant species??
Plasmid with ACC deaminase
synthases gene
Tetracycline Resistant gene
Plasmid with ACC deaminase
Deficiency mutant gene
Materials and Methods

16. Experiment Design
Two
Complementary
Experiment
Pot Experiment
Stress experiment using Cd on agar plate
(Chemical stimulating or inhibit ethylene
synthesis)

17. Pot Experiment
10 days old seedlings
transferred into pot
Saturated by mix of sand
and perlite hoagland
nutrient solution
21 Days
14 Days
Cd,
Bacterial
strain

18. Concurrent Procedure after pot experiment
1. Root colonization by the inoculated bacteria
2. Shoot ethylene measurements
 Measuring density of both bacteria in root immediately.
 Measuring ethylene level in plant shoot 24h after Cd exposure.
 Using six plant replicate in this assay.
 Plant then collected to measure plant biomass.

19. Result
 Effects of bacterial inoculation and cadmium level on plant ethylene level
 Ethylene concentrations increased with
increasing cadmium level in the soil.
 Decreased for the most extreme cadmium
contamination treatments.
 Wild-type bacterial strain on average reduced
shoot ethylene significantly from 401 to 351 pL
g−1
 Inoculation with the AcdS− mutant bacteria
increased ethylene concentration, resulting in
524 pL g−1
EthyleneConcentration
Wild Type bacteria
EthyleneConcentration
AcdS~ mutant bacteria

20.  Fresh and dry weight of A. thaliana
significantly decreased with increasing
cadmium
 At the highest cadmium concentration (250
μM), the plants showed serious symptoms of
toxicity.
 ACC deaminase-producing WT bacteria
increased plant weight compared with the
AcdS− mutant
Result
 Shoot and root fresh weight and dry weight in gradient assay

21. Result

22. Effect of mutations altering ethylene signaling on growth and stress tolerance in Arabidopsis thaliana
Result

23. Discussion
 As stress adaptation is costly, so plant growth is constrained.
 This process in plants large extent coordinated by ethylene signaling.
 Our postulation is “microbes and genetic mutations may have similar
effects on plant life history.”
 Phenotypic effects of bacteria altering plant ethylene levels are of the
same magnitude as those caused by mutation in the plant genome.

24. Research Contribution
 Resolving an important paradox related to current paradigms in plant–microbe
interactions and plant physiology.
 Bacteria harboring ACC deaminase (damage ethylene precursor) have widely been
proposed as beneficial to plants.☻
 Plant physiology studies consistently predict that lower ethylene levels will make
plants more sensitive to stress (negative). ☻
 We propose that this apparent contradiction can be harmonized if one takes plant
life history tradeoffs into account. ☻= ☻
 In this context, any change in hormonal balance will not be beneficial or
deleterious, but will instead cause a shift along existing tradeoffs(change of
another trait).
Never define relationship between growth and stress tolerance.

25. ☻ We show that ethylene reduction by mutation, chemical inhibitors, or microbiota increases
plant growth under stress-free conditions.
☻ But also comes at a cost of a hypersensitive response to stress.
☻ This effect was directly proportional to the stress level imposed.
Outcome of this research
Absence of stress, ethylene concentrations negatively correlate with plant biomass production,
Presence of a moderate stress ethylene levels positively correlate with biomass
Higher ethylene concentration Less into vegetative growth.
Highlighting the importance of this hormone as a coordinator of physiological adaptations that
allow the plant to cope with stressors.

26. A key finding
A key finding of this study is that ACC deaminase production by bacteria outside the plant
create such a strong sink for ACC that, it reduces ethylene concentration and plant stress
tolerance to a similar degree as the complete shutdown of ethylene signaling by mutations in the
plant genome (ein1eil3) or the chemical inhibition of ethylene synthesis (AIB).
In contrast, the AcdS− bacterial mutant, which indirectly induce ethylene production by
producing auxin [7], can shift the plant toward a similar stress tolerance level achieved by the
ethylene overproducer plant mutant eto1.
It is important to note that the enzyme ACC deaminase enzyme directly contributes to bacterial
fitness by allowing them to use ACC as a source of nitrogen.
AcdS− bacterial mutant = Ethylene overproducer plant mutant eto1

27. QUESTION & ANSWERS

28. Copyright: All design and figure made by Ahmed Md Robed. It is illegal to copy of them.