This document discusses microbial remediation of heavy metals from industrial wastewater. It provides an overview of factors affecting heavy metal toxicity to microorganisms, such as pH, temperature, and stability. It also describes various mechanisms microbes use to detoxify heavy metals, including biosorption, intracellular and extracellular sequestration, extracellular barriers, methylation, and reduction of metal ions. Overall, the document reviews how microbes can transform toxic heavy metals into less harmful states through metabolic and non-metabolic processes to help clean up polluted environments.
“Bioleaching" or "bio-oxidation" employs the use of naturally occurring bacteria, harmless to both humans and the environment, to extract of metals from their ores.
Conversion of insoluble metal sulfides into water-soluble metal sulfates.
It is mainly used to recover certain metals from sulfide ores. This is much cleaner than the traditional leaching.
“Bioleaching" or "bio-oxidation" employs the use of naturally occurring bacteria, harmless to both humans and the environment, to extract of metals from their ores.
Conversion of insoluble metal sulfides into water-soluble metal sulfates.
It is mainly used to recover certain metals from sulfide ores. This is much cleaner than the traditional leaching.
Hydrocarbon are major constituents of crude oil and petroleum. They can be biodegraded by naturally-occurring microorganisms in freshwater and marine environments under a variety of aerobic and anaerobic conditions. The ability of microorganisms - bacteria, archaea, fungi, or algae - to break down hydrocarbons is the basis for natural and enhanced bioremediation. To promote biodegradation, amendments such as nitrogen and phosphorous fertilizer are often added to stimulate microbial growth and metabolism
Bioremediation of heavy metals pollution by Udaykumar Pankajkumar BhanushaliUdayBhanushali111
Mechanisms and techniques used for Bioremediation which includes phytoremediation, Bacterial & fungal bioremediation. Examples of heavy metal pollution
ABSTRACT
INTRODUCTION
METHODOLOGY
BIOREMEDIATION OF OIL SPILLS
CASE STUDY
CONCLUSION
Subtopics
Bio remediation in hot and cold environments
Use of Nitrogen fixing Bacteria
Bio remediation using fungi from soil samples
Bio remediation using bacteria and case studies
Biodegradation or biological degradation is the phenomenon of biological transformation of organic compounds by living organisms, particularly the microorganisms.
Biodegradation basically involves the conversion of complex organic molecules to simpler (and mostly non-toxic) ones. The term biotransformation is used for incomplete biodegradation of organic compounds involving one or a few reactions. Biotransformation is employed for the synthesis of commercially important products by microorganisms.
Bioremediation refers to the process of using microorganisms to remove the environmental pollutants i.e. the toxic wastes found in soil, water, air etc. The microbes serve as scavengers in bioremediation. The removal of organic wastes by microbes for environmental clean-up is the essence of bioremediation. The other names used (by some authors) for bioremediation are bio-treatment, bio-reclamation and bio-restoration.
It is rather difficult to show any distinction between biodegradation and bioremediation. Further, in biotechnology, most of the reactions of biodegradation/bioremediation involve xenobiotic.
Introduction
Type of pesticides
Advantage & disadvantages of pesticides
Degradation of pesticide
Microbial degradation of pesticides
Mode of microbial metabolism of pesticides
Strategies for biodegradation
Approaches for biodegradation of pesticide
Chemical reaction leading biodegradation of pesticide
Metabolism of pesticides by MO
Metabolism of DDT
• Bioremediation – process of cleaning up environmental sites contaminated with chemical pollutants by using living organisms to degrade hazardous materials into less toxic substances
This presentation is made for S.Y.Bsc. Students.
The presentation includes Wastewater microbiology. The presentation includes information about sources as well as methods of wastewater treatment.
Bioremediation of heavy metals using Fe(III),SULPHATE AND SULPHUR reducing ba...KAVYA K N
Bioremediation of heavy metals with the help of Fe(III),Sulfate AND Sulfur reducing bacteria bacteria,environmental clean up process using geobacter and desulfuromonas species.
Hydrocarbon are major constituents of crude oil and petroleum. They can be biodegraded by naturally-occurring microorganisms in freshwater and marine environments under a variety of aerobic and anaerobic conditions. The ability of microorganisms - bacteria, archaea, fungi, or algae - to break down hydrocarbons is the basis for natural and enhanced bioremediation. To promote biodegradation, amendments such as nitrogen and phosphorous fertilizer are often added to stimulate microbial growth and metabolism
Bioremediation of heavy metals pollution by Udaykumar Pankajkumar BhanushaliUdayBhanushali111
Mechanisms and techniques used for Bioremediation which includes phytoremediation, Bacterial & fungal bioremediation. Examples of heavy metal pollution
ABSTRACT
INTRODUCTION
METHODOLOGY
BIOREMEDIATION OF OIL SPILLS
CASE STUDY
CONCLUSION
Subtopics
Bio remediation in hot and cold environments
Use of Nitrogen fixing Bacteria
Bio remediation using fungi from soil samples
Bio remediation using bacteria and case studies
Biodegradation or biological degradation is the phenomenon of biological transformation of organic compounds by living organisms, particularly the microorganisms.
Biodegradation basically involves the conversion of complex organic molecules to simpler (and mostly non-toxic) ones. The term biotransformation is used for incomplete biodegradation of organic compounds involving one or a few reactions. Biotransformation is employed for the synthesis of commercially important products by microorganisms.
Bioremediation refers to the process of using microorganisms to remove the environmental pollutants i.e. the toxic wastes found in soil, water, air etc. The microbes serve as scavengers in bioremediation. The removal of organic wastes by microbes for environmental clean-up is the essence of bioremediation. The other names used (by some authors) for bioremediation are bio-treatment, bio-reclamation and bio-restoration.
It is rather difficult to show any distinction between biodegradation and bioremediation. Further, in biotechnology, most of the reactions of biodegradation/bioremediation involve xenobiotic.
Introduction
Type of pesticides
Advantage & disadvantages of pesticides
Degradation of pesticide
Microbial degradation of pesticides
Mode of microbial metabolism of pesticides
Strategies for biodegradation
Approaches for biodegradation of pesticide
Chemical reaction leading biodegradation of pesticide
Metabolism of pesticides by MO
Metabolism of DDT
• Bioremediation – process of cleaning up environmental sites contaminated with chemical pollutants by using living organisms to degrade hazardous materials into less toxic substances
This presentation is made for S.Y.Bsc. Students.
The presentation includes Wastewater microbiology. The presentation includes information about sources as well as methods of wastewater treatment.
Bioremediation of heavy metals using Fe(III),SULPHATE AND SULPHUR reducing ba...KAVYA K N
Bioremediation of heavy metals with the help of Fe(III),Sulfate AND Sulfur reducing bacteria bacteria,environmental clean up process using geobacter and desulfuromonas species.
Sorption and transformation of toxic metals by microorganismsKhadija tul kubra
in which i discuss about the metals which are remediate by some microorganisms, these mtals poduce toxicity in the enviorment. some technologies or techniiques used to remove the heavy metals by the help of enginnered microorganisms.
Bioleaching or Metal Bioleaching or Biomining is a process in Mining and
Biohydrometallurgy (natural processes of interactions between microbes and minerals)
that extracts valuable metals from a low-grade ore with the help of microorganisms such as
Bacteria or Archaea.
• Bioleaching is an alternative to more traditional physical and chemical methods of mineral
processing.
• The application of Biomining processes predates by centuries the understanding of the role
of microorganisms in Metal extraction. However, the modern era of biomining began with
the discovery of the bacterium Thiobacillus ferrooxidans.
• Bioleaching techniques are often more effective than traditional mining applications
mechanism of bioleaching
types of bioleaching
advantages and disadvantages
Discussed about Sources of Heavy metals , Sources of Heavy metals , Bioremediation, Biosorption by Fungi, Algae, Bacteria , Factors affecting Biosorption , Heavy metals relation with human beings
Microbial Approaches In Remediation Of Metal Contaminated Soils & Aquatic sys...SDSyed
1.Microbial Approaches In Remediation Of Metal Contaminated Soils & Sediments
2.Microbial Approaches In Remediation Of Metal Contaminated Aquatic systems
Isolation of serratia liquefaciens as metal resistant bacteria from industria...IJARIIT
Sample from industry effluent consist of various metal like lead, zinc, copper, silver, mercury etc. The growth of
microorganisms is affected by various factors like temperature, PH, salinity etc. In some cases there are some microorganisms
which can tolerate the presence of metal like lead, zinc, copper, silver, mercury etc., presence of these metal is analysed by
atomic adsorption spectrometry method ,present study deals with isolation of Serratia liquefaciens is done by various
biochemical characteristics ,various parameter analysis, culturing of Serratia liquefaciens in the bacterial growth medium
which consist of artificially supplemented with metal .From the study, it is confirmed that Serratia liquefaciens is present in
the polluted water where metal dust persists in the effluent sample. Serratia liquefaciens were resistant to metal and these
microorganisms are further encouraged to degrade metal in the sample.
Phytoremediation..A cost effective and ecofriendly technique for removal of h...Soumyashree Panigrahi
This reflects light on the effects of Heavy metals on the contaminated soil & how to over come the ill effects by phyto remediation..or use of plants in reclaiming the soil...
Abstract Heavy metal pollutants are mainly derived from growing number of
anthropogenic sources. As the environmental pollution with heavy metals increases,
some new technologies are being developed, one of these being phytoremediation.
Hyperaccumulator plant varieties can be achieved by using methods of genetic
engineering. An uptake of excessive amounts of heavy metals by plants from soil
solution leads to range of interactions at cellular level which produce toxic effects
on cell metabolism in terms of enzyme activity, protein structure, mineral nutrition,
water balance, respiration and ATP content, photosynthesis, growth and morphogenesis
and formation of reactive oxygen species (ROS).On the basis of accumulation
of heavy metals plants are divided into three main types; (i) the accumulator plants,
(ii) the indicator plants, and (iii) the excluder plants. Generally, the accumulation
of heavy metals in plant organ is in series root > leaves > stem > inflorescenc >
seed. Most of plants belong to excluder group and accumulate heavy metals in
their underground parts. When roots absorb heavy metals, they accumulate primarily
in rhizodermis and cortex. In intracellular parts, highest concentration of
heavy metals is found in cell wall. Tolerance of plants against heavy metals is due
to reduced uptake of heavy metals and increased plant internal sequestration. In the
increased plant internal sequestration mechanism, plant is manifested by interaction
between a genotype and its environment. There are biochemical machineries in
plants that work for tolerance and accumulation of heavy metals. Metal transporters
are involved in metal ion homeostasis and transportation. Some amino acids and
organic acids are ligands for heavy metals and these amino acids and organic acids
play an important role in tolerance and detoxification Phytochelatins (PCs) are produced
in plants under stress of heavy metals and play role in binding heavy metals
to complexes and salts and sequestering the compounds inside the cell so that heavy
metals can not disturb the cell metabolism. The genes for phytochelatin synthesis
have been isolated and characterized. Another low molecular weight (6–7 KDa)
cysteine-rich compounds known as metallothioneins (MTs) also play an important proteins, lipids, and nucleic acids, often leading to alterations in cell structure and
mutagenesis. There are many potential sources of ROS in plants, in addition to those
that come from reactions involved in normal metabolism, such as photosynthesis
and respiration. The balance between the steady-state levels of different ROS are
determined by the interplay between different ROS-producing and ROS-scavenging
mechanisms. A variety of proteins function as scavengers of superoxide and hydrogen
peroxide. These include, among others, superoxide dismutase (SOD), catalase
(CAT), ascorbate peroxidase (APOX), glutathione reductase (GR), thioredoxin, and
the peroxiredoxin family of protein. These protein antioxidants are supplemented
with a host of non-protein scavengers, including, but not limited to, intracellular
ascorbate and glutathione. The intoxication with some heavy metals induces oxidative
stress because they are involved in several different types of ROS-generating
mechanisms.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
1. Microbial life in extreme environments
Effects of Heavy Metal on Microbial
Growth
Editor- shankar. K
Dr. Shankar K
Assisstant Profesor of Microbiology (2019-2020)
Mohmaed sathak college of arts and science,
shollignallur, chennai.
2. Resource Paper
Toxicity and Bioremediation of Heavy Metals
Contaminated Ecosystem from Tannery
Wastewater: A Review
Bernard Et al., 2018.
3. Introduction
Industrial wastewater is a major source of heavy metal
contamination in our environment. Heavy metals are the most
important pollutants in the environment.
Environmental pollution by heavy metals has become a serious
threat to living organisms in an ecosystem.
Metal toxicity is of great environmental concern because of
their bioaccumulation and non-biodegradability in nature.
Essential inorganic metals, Magnesium (Mg), Nickel (Ni),
Chromium (Cr3+), copper (Cu),Calcium (Ca), Manganese (Mn),
sodium (Na) and zinc (Zn) are vital elements needed in small
quantity for metabolic and redox functions.
4. Non essential metals, Heavy metals such as Aluminium (Al), Lead
(Pb), Cadmium(Cd), Gold (Au), Mercury (Hg), and Silver (Ag) do not
have any biological role and are toxic to living organisms.
The transformation of toxic heavy metals into a less harmful state
using microbes or its enzymes to clean-up polluted environment is
called bioremedation.
Bioremedation methods are environmentally friendly and cost-
effective in the revitalization of the environment.
Biofilm-mediated bioremediation can be applied for cleaning up of
heavy metal contaminated environment.
Microbial-metal interactions is primarily focused on metals
removal, i.e., remediation and depollution.
5. Toxicity of heavy metals to microorganisms
Toxicity of heavy metals is the ability of a metal to cause
detrimental effects on microorganisms, and it depends on the
bioavailability of heavy metal and the absorbed dose.
Heavy metal toxicity involves several mechanisms, that is,
breaking fatal enzymatic functions, reacting as redox catalysts in
the production of reactive oxygen species (ROS), destructing ion
regulation, and directly affecting the formation of DNA as well as
protein.
Factors affecting microbial remedation of heavy metals
The propensity of heavy metals to be stimulatory or
inhibitory to microorganisms is determined by the total
metal ion concentrations, chemical forms of the metals, and
related factors such as redox potential.
Factors Affecting Microbial Remediation of
6. Environmental factors like temperature, pH, low molecular weight
organic acids, and humic acids can alter the transformation,
transportation, valance state of heavy metals, and the
bioavailability of heavy metals towards microorganisms.
1. pH
Heavy metals tend to form free ionic species at acidic pH levels,
with more protons available to saturate metal-binding sites. At
higher hydrogen ion concentrations, the adsorbent surface is
more positively charged, hence reducing the attraction
between adsorbent and metal cations thereby increasing its
toxicity.
7. 2. Temperature
Temperature plays a significant role in the adsorptionof heavy
metals. Increase in temperature increases the rate of adsorbate
diffusion across the external boundary layer.
The solubility of heavy metals increases with an increase in
temperature, which improves the bioavailability of heavy metals.
The actions of microorganisms increase with rise in temperature
at a suitable range, and it enhances microbial metabolism and
enzyme activity, whichwill accelerate bioremediation.
3. Stability
The stability of microbes metal complex depends on the sorption
sites, microbial cell wall configuration, and ionization of chemical
moieties on the cell wall. The outcome of degradation process
depends on the substrate and range of environmental factors.
8. Factors that influence bioremediation of heavy metals
• Microbes
– Production of toxic metabolites, Enzymes induction, Mutation
and horizontal gene transfer Enrichment of capable microbial
populations.
• Substrate
– Chemical structure of contaminants, Too low concentration of
contaminants, Toxicity of contaminants Solubility of contaminants.
• Environmental
– Inhibitory Environmental conditions, Depletion of preferential
substrates, Lack of nutrients.
9. • Mass transfer limitations
– Oxygen diffusion and solubility, Solubility/miscibility in/with
water, Diffusion of nutrients
• Growth substrate vs. Co-metabolism
– Microbial interaction( competition, succession, and predation),
Concentration, Alternate carbon source present
• Biological aerobic vs. Anaerobic process
– Microbial population present in the site, Oxidation/reduction
potential, Availability of electron acceptors
10. Mechanism of Microbial Detoxification of
Heavy Metal
Microorganisms adopt different mechanisms to interact and survive
in the presence of inorganic metals.
Various mechanisms used by microbes to survive metal toxicity are,
o Biotransformation, Extrusion,
o Use of enzymes,
o Production of exo-polysaccharide (EPS), and
o Synthesis of metallo-thioneins.
In response to metals in the environment, microorganisms have
developed ingenious mechanisms of metal resistance and
detoxification.
The mechanism involves several procedures, together with
electrostatic interaction, ion exchange, precipitation, redox process,
and surface complexation.
11. Microorganisms can decontaminate metals by valence conversion,
volatilization, or extracellular chemical precipitation.
Microorganisms have negative charge on their cell surface because of
the presence of anionic structures that empower the microbes to
bind to metal cations.
The negatively charged sites of microbes involved in adsorption of
metal are the hydroxyl, alcohol, phosphoryl, amine, carboxyl, ester,
sulfhydryl, sulfonate, thioether, and thiol groups.
Bio Sorption
The uptake of heavy metals by microbial cells through
biosorption mechanisms can be classified into
I. Metabolism-independent biosorption,
II. Metabolism-dependent bioaccumulation.
12. Mechanisms of heavy metal uptake by
microorganisms
Bioaccumulation depends on a variety of chemical, physical, and biological
mechanisms and these factors are intracellular and extracellular processes, where
biosorption plays a limited and ill-defined role
13. Intracellular Sequestration.
Intracellular sequestration is the complexation of metal ions by
various compounds in the cell cytoplasm. The concentration of
metals within microbial cells can result from interaction with
surface ligands followed by slow transport into the cell.
Bacteria
The ability of bacterial cells to accumulate metals intracellular has
been exploited in practices, predominantly in the effluent
treatment
Cadmium-tolerant P. putida strain possessed the ability of
intracellular sequestration of copper, cadmium, and zinc ions with
the help of cysteine-rich low molecular weight proteins
Intracellular sequestration of cadmium ions by glutathione was
revealed in Rhizobium leguminosarum cells.
14. Fungi
The rigid cell wall of fungi is made up of chitin, mineral ions, lipids,
nitrogen-containing polysaccharide, polyphosphates, and proteins.
They can clean metal ions by energetic uptake, extracellular and
intracellular precipitation, and valence conversion, with several fungi
accumulating metals to their mycelium and spores.
The exterior of the cell wall of fungi behaves like a ligand used for
labelling metal ions and brings about the elimination of inorganic
metals.
Peptidoglycan, polysaccharide, and lipid are components of cell wall
that are rich in metal-binding ligands (e.g., -OH, -COOH, -HPO42−,
SO42− -RCOO−, R2OSO3−, -NH2, and-SH).
Amine can be more active in metal uptake among these functional
groups, as it binds to anionic metal species via electrostatic
interaction and cationic metal species through surface complexation.
15. Extracellular Sequestration
Extracellular sequestration is the accumulation of metal ions by
cellular components in the periplasm or complexation of metal ions
as insoluble compounds.
Copper-resistant Pseudomonas syringae strains produced copper-
inducible proteins Cop A, Cop B (periplasmic proteins), and Cop C
(outer membrane protein) which bind copper ions and microbial
colonies.
Bacteria can eject metal ions from the cytoplasm to sequester the
metal within the periplasm. Metal precipitation is an extracellular
sequestration.
Iron reducing bacterium such as Geobacter spp. and sulfur reducing
bacterium like Desulfuromonas spp. are capable of reducing harmful
metals to less or nontoxic metals.
16. G.metallireducens, a strict anaerobe, is capable of reducing manganese
(Mn), from lethal Mn (IV) to Mn (II), and uranium (U), from poisonous U
(VI) to U (IV) .
G. Sulfurreducens and G. metallireducens have the ability to decrease
chromium (Cr) from the very lethal Cr (VI) to less toxic Cr (III).
Sulfate-reducing bacteria generate large amounts of hydrogen sulfide
that causes precipitation of metal cations.
Klebsiella planticola strain generates hydrogen sulfide from thiosulfate
under anaerobic conditions and precipitated cadmium ions as insoluble
sulfides.
Cadmium was precipitated by P. aeruginosa strain under aerobic
conditions.
Vibrio harveyi strain precipitated soluble divalent lead as complex lead
phosphate salt.
17. Extracellular Barrier of Preventing Metal Entry into
Microbial Cell.
Microbial plasma membrane, cell wall, or capsule could prevent metal ions
from entering the cell.
Bacteria can adsorb metal ions by ionizable groups of the cell wall (amino,
carboxyl, phosphate, and hydroxyl groups) .
Passive biosorption of heavy metal ions is observed by nonviable cells of
Pseudomonas putida, Brevibacterium sp., and Bacillus sp.
Pseudomonas aeruginosa biofilm cells show higher resistance to ions of
copper, lead, and zinc than planktonic cells, while cells located at the periphery
of the biofilm were killed.
Extracellular polymers of biofilm accumulated metal ions and then protect
bacterial cells inside the biofilm.
18. Methylation of Metals
Methylation increases metal toxicity as a result of increased
lipophilicity and thus increased permeation across cell membranes.
Microbial methylation plays a significant function in metal
remediation.
Methylated compounds are regularly explosive; for instance, Hg (II)
canbe bio methylated by some bacteria such as Bacillus spp.,
Escherichia spp., Clostridiumspp., and Pseudomonas spp. to gaseous
methyl mercury.
Bio methylation of selenium (Se) to volatile dimethyl selenide and
arsenic (As) to gaseous arsines as well as lead (Pb) to dimethyl lead
was witnessed in polluted top soil.
19. Reduction of Heavy Metal Ions by Microbial Cell
Microbial cells can convert metal ion from one oxidation state
to another, hence reducing their harmfulness .
Bacteria use metals and metalloids as electron donors or acceptors
for energy generation.
Metals in the oxidized form could serve as terminal acceptors of
electrons during anaerobic respiration of bacteria.
Reduction of metal ions through enzymatic activity could result in
formation of less toxic form of mercury and chromium.