Project description:RNA-seq was performed to compare gene expression profiles between luminescent and low-luminescent states of Photobacterium kishitanii ANT-2200 across different growth phases. Raw RNA-seq reads were previously deposited in the NCBI Sequence Read Archive under BioProject PRJNA1464527. Processed count matrices are provided in this GEO submission.
Project description:Transcriptomic analysis of the response of Photobacterium phosphoreum and Photobacterium carnosum towards co-contaminants chicken meat.
Project description:Modified atmosphere packaging (MAP) is a common strategy to selectively prevent the growth of certain species of meat spoiling bacteria. While studies on the effectiveness of MAP are still scarce on a putative control over the population of photobacteria detected as meat spoilers, they could develop means to enhance safety and quality of raw meat. This study aims to determine the impact on photobacteria of two modified atmospheres: with high oxygen concentration (red and white meats), and free oxygen MAP (white meats and seafood). We have conducted growth experiments of the two main species found on meat, Photobacterium carnosum (P.) and P. phosphoreum, on a meat simulation media under different gas mixtures of nitrogen, oxygen and carbon dioxide representing air-, high oxygen- and vacuum-like conditions with and without carbon dioxide present. Growth was monitored based on optical density, and samples were taken during exponential growth for a comparative proteomic analysis that allowed the determination of the effects of the different gases and their synergy. Growth under air atmosphere appears optimal particularly for P. carnosum, with enhancement of energy metabolism, respiration, oxygen consuming reactions, and a predicted preference for lipids as carbon source. However, all the other atmospheres show some degree of growth reduction. An increase in oxygen concentration leads to an increase in enzymes counteracting oxidative stress for both species, and enhancement of heme utilization and iron-sulfur cluster assembly proteins for P. phosphoreum. Absence of oxygen appears to switch the metabolism towards fermentative pathways, where either ribose (P. phosphoreum), or glycogen (P. carnosum) appear to be the preferred substrates. Additionally, it promotes the use of alternative electron donors/acceptors, mainly formate and nitrate/nitrite. Stress response is manifested as enhanced expression of enzymes able to produce ammonia (e.g. carbonic anhydrase, hydroxylamine reductase) and regulate osmotic stress. Our results suggest that photobacteria do not sense the environmental levels of carbon dioxide but rather adapt to their own anaerobic metabolism. The regulation in presence of carbon dioxide is limited and strain-specific under anaerobic conditions. However, when oxygen at air-like concentration is present together with carbon dioxide the oxidative stress appears enhanced compared to air conditions (very low carbon dioxide), explained if both gases have a synergistic effect. This is further supported by the increase in oxygen concentration in presence of carbon dioxide. The atmosphere is able to fully inhibit P. carnosum, heavily reduce P. phosphoreum growth in vitro and trigger diversification of energy production with higher energetic cost, highlighting the importance of concomitant bacteria for their growth on raw meat under said atmosphere.
