1

Microorganisms & Biogeochemical Cycles

� Biogeochemical Cycles:

– Movement & transformation of chemical elements (nutrien) in

the environment caused by biological and chemical

processes in the atmosphere, hydrosphere & lithosphere

� Both macro and micronutrients go through

biogeochemical cycles

� Why do biogeochemical cycles happen?

� What is the role of microorganisms in biogeochemical

cycles?

� Biogeochemical cycles happen as natures effort for :– Prevent accumulation of waste

– Maintain availability of nutrients needed by the enviroment/ecosystem

� The biogeochemical cycle is a global cycle � impacts the geology and earth environment as a whole

� Naturally, the chemical elements are in a balance

� Human activities change/disrupt the balance of the elements (example: C cycle)

2

Biogeochemical Cycle

3

The Microorganism and Biogeochemical

Cycles

� The role of microorganisms in nature: decomposer

� Microorganisms are biological agents directly involved

in biogeochemical cycles

� Microorganisms are sources for some elements and

reservoirs for other elements

� Interaction among microorganisms, humans and other

parts in the biosphere create global problems

Biological contribution on Atmosphere

Composition

negligibleMicroorg, animalsMicroalgae

Plants

O2

+0,3%Microorg (?),

Chemicals (?)

Microorg (50), Humans

(50)

N2O

+1%Microorg,

chemicals

Microorg(26), Animals

(17), Humans (57)

CH4

+0,4%Microalgae

Plants

Microorg(86), Animals,

Humans

CO2

Humans (41)Microorg (53)Microorg (100)N2

% changeRemovalInput fromType of Gas

4

Carbon Cycle (C) & Oxygen (O)

� The C Cycle cannot be separated from the O cycle:– CO2 fixation

– Organic substance oxidation � CO2

� Global transfer of C occurs in the form of CO2 (most active reservoir)

� The C cycle involves activity of micro- and macro-organisms

� Main role of microorganisms: DECOMPOSER organic substances

Global C Cycle

5

Main Stages of the C Cycle

� Photosynthesis:

– Organic C production by autotrophs

� Degradation /Decomposition:

– The utilization of organic C organik by microorganisms, forming:• CO2

• CH4

– Microorganisms that play a role: Heterotrophic, Methanogens

Disturbance of C Cycle: Greenhouse Effect

� Greenhouse effect:– Increase in environment temperature because of increase in

atmospheric CO2

� The reason for increased CO2?– Increased human activities (domestic, industry, etc) �

increased CO2 emission

� Reducing CO2 emission?– Limiting emission � not economical

– Social impacts � Kyoto Protocol 1997

� Increase global temperature � increase in disease incidence

6

Relation of temperature increase & disease

incidence

Global warming

Precipitation Ocean surface temperature

Nutrient availability Phytoplankton

Vibrio cholerae Zooplankton

Cholera incidence

Nitrogen Cycle

� Availability of nitrogen in the environment: in several oxidation states

� N2 is the highest concentration of gas in the atmosphere

� Processes in N cycles:– Nitrification

– Denitrification

– Nitrogen Fixation

– Ammonification� Aerobe & anaerobe

� All above processes require microorganisms

7

N2

NH4+

Nitrogen

fixation

NO2 -ammonium oxidation

NO3 -

Nitritoxidation

NO2-

Dissimilative NO3 - reduction

Assimilative NO3- reduction

R-NH2

Ammonification

ammonium assimilationNitrite

ammonifcation

NO

denitrification

N2O

Nitrogen Cycle

Utilization of N Cycle

� Research on N cycle is very active:

– Capability of bacteria for N fixation � efforts to reduce use

anorganic N fertilizer

– Isolation of anammox bacteria (anaerobic ammonia

oxidation) � transform N component of liquid waste into N2

� Development of inoculum for N fixation commercially

� Indonesia: “Rhizoplus”

8

Iron Cycle (Fe)

Fe(III)

Plaque

Fe(II)

solute

organic C CO2

Reduction

Oxidation

Metabolism

Anaerobe

Reductive bacteria Fe(III)

Metabolism

Aerobe

Oxidative bacteria Fe (II)

O2H2O root

Sulphur Cycle

• redox reaction

• Microorganism: Beggiatoa,

Thiothrix, Thiobacillus

• Gradient microorganism:

• lives on the interface of

anaerobic environment,

sediment, & oxygenated

water.

9

H2S S0

Oksidasi sulfida

SO42-

R-SHReduksi sulfat

asimilatif

Desulfurisasi

Reduksi sulfat

disimilatif

Respirasisulfur

Oksidasifototrofik

S0

Oksidasi fototrofik

Aerob

Anaerobe

Bio corrosion: interaction between the S and

Fe Cycle

� Occurrence of S cycle can cause corrosion of

steel (Fe) pipes on soil that contains S

� The reaction:– Fe0 + H2O � Fe(OH)2 + H2

– 4H2 + SO42- � H2S + 2OH

- + 2H2O

– H2S + Fe 2+ � FeS + H2

10

Acid Rain

� The Acid Rain phenomenon: H2SO3 & H2SO4

� Acid rain can damage buildings & monuments

made from marble & limestone

� How to prevent acid rain?

Origins of Acid Rain