Abstract
Bacterial infection presents severe challenge to tilapia farming, which is largely influenced by water temperature. However, how water temperature determines tilapias’ survival to infection is not well understood. Here, we address this issue from the perspective of metabolic state. Tilapias were more susceptible to Aeromonas sobria infection at 33°C than at 18°C, which is associated with differential metabolism of the fish. Compared to the metabolome of tilapia at 18°C, the metabolome at 33°C was characterized with increased an tricarboxylic acid cycle and a reduced level of myo-inositol which represent the most impactful pathway and crucial biomarker, respectively. These alterations were accompanied with the elevated transcriptional level of 10 innate immune genes with infection time, where il-1b, il-6, il-8, and il-10 exhibited a higher expression at 33°C than at 18°C and was attenuated by exogenous myo-inositol in both groups. Interestingly, exogenous myo-inositol inactivated the elevated TCA cycle via inhibiting the enzymatic activity of succinate dehydrogenase and malate dehydrogenase. Thus, tilapias showed a higher survival ability at 33°C. Our study reveals a previously unknown relationship among water temperature, metabolic state, and innate immunity and establishes a novel approach to eliminate bacterial pathogens in tilapia at higher water temperature.
Highlights
GIFT is one of the most extensively farmed economic fish species in the world due to its high protein content, large size, rapid growth and great adaptability to a wide range of rearing conditions [1, 2]
To investigate the effect of water temperature on tilapias’ ability against bacterial infection, tilapia were cultured at 18°C or 33°C and challenged with 1 × 105 CFU of A. sobria, which is an LD50 dose obtained in pretest
The survival rate of the fish was 86.67% and 50% at 18°C and 33°C, respectively (Figure 1). These results indicate that tilapias are more susceptible to A. sobria infection at 33°C than at 18°C
Summary
GIFT (genetically improved farmed tilapia, Oreochromis niloticus) is one of the most extensively farmed economic fish species in the world due to its high protein content, large size, rapid growth and great adaptability to a wide range of rearing conditions [1, 2]. The animal is cultured in more than 100 tropical and subtropical countries, and thereby fishing productivity is improved and the development of aquaculture is facilitated in the world [3, 4]. Tilapia accounts for 7.4% of global production in 2015, the demand for tilapia is increasing in recent years. Many countries in Asia, Africa, and Latin America expand the tilapia farming for driving the global growth. China is the biggest producer and exporter of the fish, accounting for around 26% of total supply in 2019. In 2020, an increase of 3%–4% compared to 2018 is obtained, which increases
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