Document Type

Thesis

Date of Award

8-2020

School/College

College of Science, Engineering, and Technology (COSET)

Degree Name

MS in Biology

Committee Chairperson

Jason Rosenzweig

Committee Member 1

Daniel Vrinceanu

Committee Member 2

Hector Miranda

Committee Member 3

Shishir Shishodia

Keywords

bacteria, bio aerosols, house dust, indoor dust microbiota

Abstract

House dust is a complex matrix containing organic and inorganic content with a good percentage of microorganisms. Microorganism’s growth and survival in dust depends on available moisture level. Microbial origin in dust depends on sources other than dust. On average people spend approximately 90% of their time in indoor environment. Therefore, they are continuously exposed to microbes in dust. Based on the size and volume of dust particles the microbes get access to human lungs via airways. Based on previous research; culture dependent studies indicate that Penicillium, Aspergillus, Cladosporium are in abundance is house dust along with 20 other fungal genera. While bacterial flora in house dust is dominated by gram positive bacteria such as Staphylococcus, Corynebacterium, and Lactococcus etc. Culture-independent studies demonstrate that higher diversity of fungal and bacterial species, approximately 500-1000 species is prevalent in house dust. Microbial abundance in house dust can exceed up to 109 cells/g dust, depending on techniques employed, different environmental conditions and type of indoor environment, among other factors. In current study filter dust samples were collected from ten households from Houston by volunteers by following the devised protocol and assessed for diversity and bacterial abundance in indoor air. Samples were transported and stored in labs before processing. Samples were processed by following two techniques i.e. Cut sample technique and Serial dilution. The bacterial colonies were grown on three different media i.e. Luria-Bertani", Eosin Methylene blue and MacConkey agar. The pure colonies were counted with serial dilution technique . The next step was bacterial identification. Microbes were identified using Morphological characteristics, Gram staining, Oxidase, Catalase test and Biolog technique. Ten bacterial strains were identified by using Biolog technique on the basis of their metabolic potential. All bacteria isolated and identified were found to be Gram positive in nature. Bacillus cereus was selected as an organism of interest because of its pathogenicity against humans. Therefore, ATTC strain of B. cereus was obtained and growth kinetics and biofilm production was compared to investigate the survival potential of surrogate bacteria when exposed to lead challenge (0.5ppm,10ppm, 25ppm and 100ppm). The statistical analysis indicated higher growth rate and biofilm production of B.cereus isolated from indoor filter dust sample when exposed to different concentrations of lead (Pb) in comparison to an ATTC strain of B.cereus.

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