A research proposal on plant-microbe species in relation to heavy metals contents of soils around an iron smelting company.

Either naturally or due to anthropogenic factors, the ecosystem is in a constant state of flux. The inherent characteristic of the ecosystem to return to its stable form after a period a regime of disturbance is what has been defined as the ecosystem resilience (Holling, 1973). This ability is conferred on the ecosystem as a result of the numerous plant, animal and microbial diversity. The biological diversity or biodiversity which has been defined as the totality of living organisms present within the ecosystem (Convention on Biological Diversity, 1992) provide important processes that tend to keep the system in a stable form in the absence of disturbance or returns the system to stable form after a disturbance regime. Processes such as decomposition, nutrient cycling, productivity and energy are carried out by living organisms in the ecosystem because it directly or indirectly relates to their own existence within the ecosystem.

^{A grassland ecosystem (source: pxhere CC0)}

Disturbance to the ecosystem can be in different forms. For example, a forest ecosystem can be disturbed as a result of wildfire (which could be anthropological or natural), storm, logging, lumbering, hunting, farming, fruit and fuel-wood gathering among other factors. An aquatic environment could be disturbed as a result of nutrient enrichment (eutrophication), fishing, thermal deposition and a host of other factors.

There is no doubt that anthropological or man-made disturbance is the leading cause of the instability of the ecosystem. One of such disturbances is pollution of the environment by heavy metals. According to Tchounwou et al. (2012), heavy metals refer to elements which naturally occur in the universe and characterized with high atomic weight and a density of at least 5 times that of water. They serve numerous important use to man and his activities including in the area of medicine, agriculture, mining, manufacturing, etc. Consequently, they have become widely dispersed and are found in varying degree of concentrations within the environment where they sometimes get into the food chains depending on their bioavailability, causing environmental and health havocs at above certain concentration threshold. Below, the threshold, some of them have actually been reported to serve important functions in the body of living organisms (Asati et al., 2016).

^{Environmental pollution (source: Nils Ally, CC BY 3.0)}

Heavy metal toxicity in biological diversity and their associated effects have been studied by researchers in various parts of the world, although a large percentage of these studies focused on humans. Jaishankar et al. (2014) in their review of the mechanisms and health effects of some heavy metals in relation to the human body opined that the metals while acting as pseudo-nutrient in the body often interfere with important metabolic processes that sustain human’s life. This mechanism of operation and effects have also been reported to be applicable to other living organisms, including plants (Asati et al., 2016) and microbes (Wang et al., 2006).

However, biological organisms show varying degrees of tolerance to heavy metal ranging from absolute intolerance to high degree of tolerance. While some have device means of excluding the elements in their system by creating extracellular barriers to the metals, some have the capacity to bio-accumulate the metals over a long period of time without showing any visible injury symptom while a host of others have different other means of tolerating the metals. For example, some plants’ tolerance for heavy metals have been reported to be due to different mechanisms such as the restriction of heavy metals by association of their tissues with mycorrhiza, binding of heavy metals with plant cell wall and root excretions, metal efflux from the plasma membrane, metal chelation by phytochelatins and metallothioneins, and compartmentalization within the vacuole (Kushwaha et al., 2015). In addition, mechanisms such as extracellular barrier creation, active transport of metal ions, extracellular sequestration, intracellular sequestration and reduction of metal ions have been reported in bacteria. All these mechanisms are either naturally inherent in the organisms or evolved as a form of adaptation to heavy metal contamination of the environment where such organisms found themselves.

Over the years, plants and microbes with the unique capacity to tolerate heavy metals have been studied by various researchers with a view to exploiting them for the purpose of ridding the environment of heavy metal contaminants, especially those with bio-accumulating ability. In a particular study by Tsekova et al. (1998), Rhizopus delemar, Penicillium brevicompactum and Saccharomvces cerevisiae were found to have high heavy metal absorbing capacity. Generally, sites or habitats with heavy metal contamination are known to be major sources of metal tolerant plants, animals and microbial species. The metal tolerant species can serve as potential candidates in the process of decontaminating natural or anthropological contamination of the environment with heavy metals.

Hence, this study is going to be aimed at identifying plant and soil microbial diversity associated with the vegetation surrounding an iron and steel production company located in Ile-Ife, Osun State, here in Nigeria. The specific objectives of this research would include but not limited to;

• Identification and enumeration of plant species in the sample plots which will be located around the iron and steel company
• Isolation and presumptive identification of bacterial and fungal species associated with the soils within the sample plots
• Structure and heavy metal analysis of the soils within the sample plots.

References

• Holling, C.S. (1973). "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics. 4: 1–23.

• Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2012). Heavy metal toxicity and the environment. Experientia supplementum (2012), 101, 133-64.

• Convention on Biological Diversity (1992). Secretariat of the Convention on Biological Diversity, Montreal, Canada

• Jaishankar, M., Tseten, T., Anbalagan, N., Mathew, B. B., & Beeregowda, K. N. (2014). Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary toxicology, 7(2), 60-72.

• Ambika Asati1 , Mohnish Pichhode2 and Kumar Nikhil3. 2016. Effect of Heavy Metals on Plants: An Overview. International Journal of Application or Innovation in Engineering & Management. Volume 5, Issue 3

• YuanPeng Wang, JiYan Shi, Hui Wang, Qi Lin, XinCai Chen, YingXu Chen. 2007 The influence of soil heavy metals pollution on soil microbial biomass, enzyme activity, and community composition near a copper smelter. Ecotoxicology and Environmental Safety Volume 67, Issue 1, Pages 75-81

• K. Tsekova, A. Kaimaktchiev & A. Tzekova (1998) Bioaccumulation of Heavy Metals by Microorganisms, Biotechnology & Biotechnological Equipment, 12:2, 94-96

• Kushwaha, Anamika & Rani, Radha & Kumar, Sanjay & Gautam, Aishvarya. (2015). Heavy metal detoxification and tolerance mechanisms in plants: Its implications for Phytoremediation. Environmental Reviews. 24. 10.1139/er-2015-0010.

• Ianieva, Olga. (2009). [Mechanisms of bacteria resistance to heavy metals]. Mikrobiolohichnyĭ zhurnal (Kiev, Ukraine : 1993). 71. 54-65.