Investigating beneficial microbes from marsh ecosystems for sustainable agricultural and environmental applications
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INVESTIGATING BENEFICIAL MICROBES FROM MARSH ECOSYSTEMS FOR SUSTAINABLE AGRICULTURAL AND ENVIRONMENTAL APPLICATIONS
Petrina Tanesha McKenzie-Reynolds
Faculty Advisor: Dr. Gulnihal Ozbay
ABSTRACT
Microorganisms are often thought of as pests and harmful organisms, but there are numerous important microbes that are beneficial to both human and environmental health. Some microbes develop symbiotic associations with plants helping in their growth and survival while many others develop resistance to metals toxicity and remove them from our soils and water. Effective and efficient bioaccumulation of soluble and particulate forms of metals by microorganisms can be implemented to reduce heavy metal environmental pollution. Reports on global climate change also predicts in loss of 50% of arable land worldwide due to increased salinity, indicating the need for sustainable agriculture. These threats have inspired the need for use of these environmental friendly microbes in amending these issues. For these reasons, this study was focused on studying microorganisms from tidal marsh zones with special attention on heavy metal tolerant bacteria and mycorrhizae from the Blackbird Creek Marsh, located in Townsend, Delaware. We assume that the stressors in marsh might enhance the development of mycorrhizae with special abilities to withstand these conditions. These marsh ecosystems are exposed to various abiotic/biotic stresses such as tidal inundations, temperature, salinity and excess nutrients and naturally they harbor these microorganisms that can remove excess heavy metals accumulated in these soils. For the isolation of lead and cadmium tolerant bacteria, soil samples were inoculated in Luria Broth (LB) and enriched with various concentrations of lead nitrate and cadmium chloride. Heavy metal tolerant bacterial colonies were enumerated and genomic DNA was isolated using phenol: chloroform method. DNA was amplified using universal bacterial primers (27F/ 1492R) and the PCR amplicon was identified by Sanger sequencing.
Growth of bacteria tolerating high levels of lead (concentrations up to 2500 mg/kg) and cadmium (up to 500 mg/kg) was observed.
Most of the bacteria identified are 97% similar to the cadmium tolerant aerobic bacteria, Bacillus cereus. Analysis also identified Enterobacter Sp. to be 98% similar to most of the lead tolerant bacteria. A pilot plant study was conducted through greenhouse experiments, and marsh soils were used to grow S. alterniflora. The soils were autoclaved to kill the spores. Salinity treatments were conducted, and plant measurements were recorded both for the treatment and control samples. Positive VAM effect was observed especially in the root masses of the harvested Spartina plants. Root samples from S. alterniflora were collected and stained with acid fuschin. They were also observed under light microscope which confirmed the presence of mycorrhizal spores. Nested PCR confirmed the Mycorrhizae present in the samples belonging to the Glomus, Aculospora, Archaeospora, Gigaspora and LETC groups.
Keywords: Mycorrhizae, symbiosis, heavy metals, bacteria, marsh wetlands, sustainable, Spartina alterniflora, Phragmites australis, bioremediation