Food Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India.
Life Sciences, Homi Bhabha National Institute (Deemed to be University), Mumbai, India.
Arch Microbiol. 2023 Apr 17;205(5):197. doi: 10.1007/s00203-023-03528-6.
The cAMP receptor protein (CRP) is a global regulatory protein. We evaluated the role of CRP in starvation physiology in Salmonella Typhimurium. The Δcrp mutant survived 10 days of starvation. However, in a co-culture with the wild type in nutrient-rich medium, Δcrp died within 48 h. Similar co-culture results were observed with Escherichia coli and Staphylococcus aureus. Our study showed that the Δcrp mutant was not killed by toxins and the Type IV secretion system of the WT. The possibility of viable but non-culturable cells (VBNC) was also ruled out. However, when the overall metabolism of the co-culture was slowed down (anaerobic condition, inhibition by antibiotics and low temperature) that improved the survival of Δcrp in co-culture. But one more significant observation was that the Δcrp mutant survived in nutrient-free co-culture conditions. These two observations suggest that CRP protein is essential for efficient nutrient assimilation in a competitive environment. The cells without CRP protein are unable to evaluate the energy balance within the cell, and the cell spends energy to absorb nutrients. But the wild type cell absorbs nutrients at a faster rate than Δcrp mutant. This leads to a situation wherein the Δcrp is spending energy to absorb the nutrients but is unable to compete with the wild type. This futile metabolism leads to death. Hence, this study shows that CRP is a metabolism modulator in a complex nutrient environment. This study also highlights the need for innovative growth conditions to understand the unique function of a gene.
环磷酸腺苷受体蛋白（CRP）是一种全局调控蛋白。我们评估了 CRP 在鼠伤寒沙门氏菌饥饿生理中的作用。Δcrp 突变体在饥饿 10 天后仍能存活。然而，在营养丰富的培养基中与野生型共培养时，Δcrp 在 48 小时内死亡。在大肠杆菌和金黄色葡萄球菌中也观察到了类似的共培养结果。我们的研究表明，Δcrp 突变体不会被 WT 的毒素和 IV 型分泌系统杀死。也排除了活但非可培养细胞（VBNC）的可能性。然而，当共培养的整体代谢减缓（厌氧条件、抗生素抑制和低温）时，Δcrp 在共培养中的存活得到改善。但更重要的观察是，Δcrp 突变体在无营养的共培养条件下存活。这两个观察结果表明，CRP 蛋白对于在竞争环境中有效吸收营养物质是必不可少的。没有 CRP 蛋白的细胞无法评估细胞内的能量平衡，细胞会消耗能量来吸收营养物质。但是野生型细胞吸收营养物质的速度比 Δcrp 突变体更快。这导致了一种情况，即 Δcrp 正在消耗能量来吸收营养物质，但却无法与野生型竞争。这种徒劳的代谢导致死亡。因此，本研究表明 CRP 是复杂营养环境中的代谢调节剂。这项研究还强调了需要创新的生长条件来理解基因的独特功能。
