Abstract
Rhodobacter sphaeroides is a purple non-sulfur bacterium that belongs to the α-3 subdivision of Proteobacteria. R. sphaeroides is a model bacterial species because of its complex genome structure and expanded metabolic capabilities. The genome of R. sphaeroides consists of two circular chromosomes and five endogenous plasmids. It has the ability to grow under a wide variety of environmental conditions. It grows aerobically (~20% O2), semi-aerobically (~2% O2), and photosynthetically (under anaerobic condition plus light). It has been previously shown that many bacterial species utilize a number of alternate carbon sources for their optimal growth under a variety of growth conditions. We hypothesize that different or an additional carbon source in the minimal medium differentially affects the bacterial growth under dark-aerobic conditions. The bacterial growth kinetics and the number of cells in the bacterial culture were analyzed by measuring the optical density (OD at 600 nm) and the colony forming units (CFUs) at regular intervals of bacterial cultures. Results reveal that sodium succinate is the preferred sole carbon source for the optimal growth of R. sphaeroides. The results of growth kinetics and CFUs together concluded that from the tested carbon sources, sodium succinate is the best single carbon source in the minimal media for the optimal growth of R. sphaeroides. Interestingly, cell culture grown in SIS supplemented with sodium acetate exhibits a prolonged lag phase with the lowest ODs and CFUs that later switches to the growth-burst phase support previously discovered similar phenomenon of the growth-rate switch in the presence of acetate metabolism. Future work will utilize the aerobically grown R. sphaeroides’ cells as a biocatalyst to deplete the oxygen levels from natural gas streams and industrial gas pipelines.
Highlights
Around the world and in the United States, the corrosion of natural gas pipelines has been causing millions of dollars to be wasted each year, and is an important issue of economic concern [1]
The results of Optical Density (OD) and colony forming units (CFUs) for the bacterial cultures grown in the minimal media with a single carbon source are shown in Figure 1(a) and Figure 2(a), respectively
Results exhibit that the ODs reflecting the cellular biomass over a continuous time-course of the bacterial cultures grown in the media with sodium succinate are significantly higher (p < 0.01) than the ODs of the bacterial cell culture grown in either sodium pyruvate or sodium acetate
Summary
Around the world and in the United States, the corrosion of natural gas pipelines has been causing millions of dollars to be wasted each year, and is an important issue of economic concern [1]. In order to develop environmentally- and eco-friendly methods to deplete oxygen from the gas pipelines and natural gas streams, Rhodobacter sphaeroides and other related species can be utilized as biocatalysts [2]. R. sphaeroides grows in a variety of laboratory growth conditions, which include aerobic (~20% O2), semi-aerobic (~2% O2), anoxygenic photosynthesis under light, and anaerobic growth conditions [4]. Using R. sphaeroides as a biocatalyst to prevent the corrosion of gas pipelines has a variety of advantages. R. sphaeroides will grow in conditions that mimic the growth parameters of the gas pipeline system. This includes growing the bacterium in dark-aerobic conditions and a nearly neutral pH. This study is designed to develop a minimal media in which R. sphaeroides can grow optimally under dark aerobic growth conditions.
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