Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Marjorie Holland

Relational Format



The Mississippi vegetated coastal wetlands consist of many salt and brackish marshes. In those marshes, there are two plant species Spartina alterniflora and Juncus roemerianus that thrive in those environments. This would not be possible without the benefits of microbial communities that live in the portion of the plant's soil called the rhizosphere. The rhizosphere is crucial for plant nutrition, health, and quality. It supports the biomass and activity of microorganisms for carbon sequestration, ecosystem functioning, and nutrient cycling in natural ecosystems. To investigate the vegetation effects on rhizosphere microbial communities in coastal wetlands, plant samples and their rhizosphere soils were collected from two brackish transects and two saltwater transects at Graveline Bayou, Gautier, MS. A number of biotic and abiotic factors were measured, and their impacts on bacterial community composition and diversity were determined via Illumina MiSeq 16S rRNA gene sequence. Overall, the composition of rhizosphere bacterial community in coastal wetlands were dominated by Proteobacteria and Planctomycetes. The effects of seasonal patterns and plant developmental stages had no impacts on rhizosphere microbial communities due to similar pH level, soil moisture, and organic matter content in soil between winter and summer seasons of 2015. Salinity increased bacterial community diversity especially Proteobacteria and Bacteroidetes. There are several contrasting reports that portrayed the dominant factor in determining the diversity of rhizosphere microbial communities as either the plant species itself or the soil type of the site. In this study, the soil type was the major driving force in bacterial community diversity.

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