论文标题
测量细菌的低频电荷噪声
Measurement of the Low-Frequency Charge Noise of Bacteria
论文作者
论文摘要
细菌细节调节其细胞内离子浓度，并在整个细菌膜上产生离子浓度梯度。这些离子浓度梯度为许多细胞过程提供了自由能，并通过跨膜运输维持。鉴于细菌的物理尺寸和跨膜转运中的随机性，细胞内离子浓度且细菌的电荷状态必将波动。在这里，我们通过将凝聚态物理学的电测量技术与微流体化合物结合使用，研究了100s非运动细菌的电荷噪声。在我们的实验中，微通道中的细菌由于离子的随机流入和外排而在嵌入电解质中产生电荷密度波动。这些电荷密度波动被发现为电阻噪声，频率的频谱密度为频率成比例为$ 1/f^2 $的频率$ 0.05〜 {\ rm Hz} \ leq f \ leq f \ leq f \ leq 1〜 {\ rm hz} $。适合简单的噪声模型表明，细菌的稳态电荷在$ \ pm 1.30 \ times 10^6 {e}〜（{e} \大约1.60 \ times 10^{ - 19}〜{\ rm c}）$中，表明细菌固定型和良好的噪声是强大的噪声。然后，RMS电荷噪声可用于估计膜电位的波动。但是，由于我们对细胞内浓度梯度的理解有限，估计值不可靠。
Bacteria meticulously regulate their intracellular ion concentrations and create ionic concentration gradients across the bacterial membrane. These ionic concentration gradients provide free energy for many cellular processes and are maintained by transmembrane transport. Given the physical dimensions of a bacterium and the stochasticity in transmembrane transport, intracellular ion concentrations and hence the charge state of a bacterium are bound to fluctuate. Here, we investigate the charge noise of 100s of non-motile bacteria by combining electrical measurement techniques from condensed matter physics with microfluidics. In our experiments, bacteria in a microchannel generate charge density fluctuations in the embedding electrolyte due to random influx and efflux of ions. Detected as electrical resistance noise, these charge density fluctuations display a power spectral density proportional to $1/f^2$ for frequencies $0.05~{\rm Hz} \leq f \leq 1 ~{\rm Hz}$. Fits to a simple noise model suggest that the steady-state charge of a bacterium fluctuates by $\pm 1.30 \times 10^6 {e}~({e} \approx 1.60 \times 10^{-19}~{\rm C})$, indicating that bacterial ion homeostasis is highly dynamic and dominated by strong charge noise. The rms charge noise can then be used to estimate the fluctuations in the membrane potential; however, the estimates are unreliable due to our limited understanding of the intracellular concentration gradients.
