ECOLOGY

by Purwaning Rohmah/BIO off A 2015 UM

BIOINDICATOR:

Bacteria as Indicator of Environmental Pollution

1.      Heavy Metal Pollution

Thiobacillus sp. is pollution indicator for mercury (Hg) in marine environment. These bacteria oxidize toxic Hg. These Hg ions enter the food chain and hazard the human. The water-soluble mercury ions (Hg²⁺) are toxic. These bacteria change the sulfide mercury into mercury ions.

Thiobacillus sp. advanced mechanisms will convert Hg²⁺ into methyl mercury (CH₃-Hg) and dimethyl-mercury (CH₃-Hg-CH₃) through oxidation process. Methylation process requires vitamin B12 as coenzyme. Methyl mercury and dymethyl mercury are stored in fat layers. Methyl mercury is 100 times more toxic than Hg⁺ or Hg²⁺. Sulfide (HgS) called cinnabar is the main form of mercury ore. HgS is primary form of Mercury which can be found in anaerobic environments. HgS will be oxidized by Thiobacilli then formed mercury ions (Hg²⁺) through the aeration process. The Hg²⁺ is soluble in water and is toxic.

Further, periplasmic protein Hg²⁺ found in Pseudomonas sp. trapping protein that has the ability to bind mercury ions. The principe is that Hg²⁺ bound between two cysteine residues in proteins and form R-S-Hg-S-R bonds. Then, mercury ions are transferred through the plasma membrane, and soon turns into Hg⁰⁺. This mechanism prevent the incorporation of Hg²⁺ free ions with cysteine or other proteins that can cause protein denaturation. Several studies have been performed using Pseudomonas sp. as an indicator of mercury pollution in the sea.

There is also Serratia marcescens as an indicator for pollution of Cd and Pb. Cristani et al. found that S. marcescens can be used in the bioremediation process of toxic metals. Other studies have shown that Thiobacillus sp. can also be an indicator of the Pb pollution in the environment and Vibrio sp. as an indicator of heavy metal pollution in the sea

Picture 1. Mercury Cycle in the environment (Modification of Ijong). Cycle of mercury divided in three phase: sediment, water and atmosphere: 1) Mercury cycle began at aquatic sediments in the form of HgS and transformed into  Hg ²⁺ and  Hg⁰ ions by bacteria, to be transformed into methyl mercury and dimethyl mercury by bacteria through the oxidation process. 2) Methyl mercury accumulated in fish through the food chain. 3) Dimethyl mercury from water oxidation can be directly released into the atmosphere or through the photochemical process of  Hg⁰ and CH₄.

2.      Faecal Contamination

Coliform bacteria

A study using coliform bacteria and Streptococcus sp., as an indicator of fecal pollution in coastal areas. In addition to coastal area, coliform can also be used as indicator of human fecal pollution in lakes, rivers, beaches, estuaries and the organisms within, e.g. fishes.

Fecal indicator bacteria found in lakes, ponds and rivers as parts of the living environment. As long as the fecal coliform bacteria are in low level, then the swimming activity is relatively safe. In contrast, if the bacteria found in drinking water, it is a warning that should be taken for next consideration for fast response. Coliform is common indicator for quality of food and water sanitation. Coliform can be found in the aquatic environment, soil and vegetation. These bacteria are commonly present in large quantities in warm-blooded animal feces. However, coliform itself usually does not cause serious illness.

A number of studies have found that Streptococcus sp. as an indicator of fecal pollution in sewage treatment ponds, high rate oxidation ponds in wastewater treatment, coastal, Ganga and Cauvery River India. While, Vibrio sp. is an indicator of fecal pollution in the water and sediment of lake.

Escherichia coli is an indicator of humans and animals fecal contamination in lake’s sediments, organic wastewater, lagoon (artificial pond), rivers, urban areas and river banks, coastal recreation waters, subtropical waters and its sediment. Further, these bacteria are found in water sources of Alpine mountains, wild animals such as wild pigeons, regional water reclamation facilities, and beach.

Generally Vibrio sp. is mostly found in the estuary, sea water, river estuaries and the marine sediment particles. It is often contaminate seafood such as shrimp, fish, crabs, clams, lobster etc. These bacteria are rapidly growing in the tropical area, especially in dry season. Vibrio parahaemolyticus were found in the waters of the bay of Manado, Tasik Ria and the waters surround Bunaken Island.

3.      Wastewater Pollution

 

Several studies have been conducted to evaluate the quality of the environment by using bacteria as an indicator of household waste water pollution in tropical estuaries and reclamation water. Heterotrophic bacteria, coliform, Streptococcus sp., and Pseudomonas aeruginosa was found as an indicator of wastewater contamination. In addition, Salmonella spp. and Streptococcus sp. can be used as an indicator of bacterial contamination in the wastewater tropical estuaries as well.

4.      Oil and Pentachlorophenol Pollution

One study found that Chromatium sp. can acts as be bio-indicators for environmental contamination of crude oil. Moreover, it was found that Bacillus subtilis is an indicator of toxicity and pentachlorophenol existence (organochlorine compounds used as pesticides and disinfectants).

Source: 

Sumampouw, Oksfiriani Jufri., Yenni Risjani. 2014. Internatoional Journal of Ecosystem. Bacteria as Indicators of Environmental Pollution, 4 (6): 251-258.