A submersible, off-axis holographic microscope for detection of microbial motility and morphology in aqueous and icy environments

Sea ice is an analog environment for several of astrobiology’s near-term targets: Mars, Europa, Enceladus, and perhaps other Jovian or Saturnian moons. Microorganisms, both eukaryotic and prokaryotic, remain active within brine channels inside the ice, making it unnecessary to penetrate through to liquid water below in order to detect life. We have developed a submersible digital holographic microscope (DHM) that is capable of resolving individual bacterial cells, and demonstrated its utility for immediately imaging samples taken directly from sea ice at several locations near Nuuk, Greenland. In all samples, the appearance and motility of eukaryotes were conclusive signs of life. The appearance of prokaryotic cells alone was not sufficient to confirm life, but when prokaryotic motility occurred, it was rapid and conclusive. Warming the samples to above-freezing temperatures or supplementing with serine increased the number of motile cells and the speed of motility; supplementing with s...

海冰是天体生物学近期若干探测目标的类比环境：火星、木卫二（Europa）、土卫二（Enceladus），以及其他可能的木星或土星卫星。真核与原核微生物均可在冰内的盐水通道中保持活性，这意味着无需穿透冰层抵达下方液态水即可探测生命。我们研发了一款可潜入式数字全息显微镜（submersible digital holographic microscope, DHM），其分辨率可达单个细菌细胞级别，并已验证其可直接对格陵兰努克（Nuuk）附近多个点位采集的海冰样本进行实时成像。在所有样本中，真核生物的形态与运动性均为确凿的生命活动指征。仅依靠原核细胞的形态不足以确认生命存在，但当原核生物出现运动性时，则可快速且确凿地证明生命活动。将样本加热至冰点以上或添加丝氨酸（serine）可提升运动细胞的数量与运动速率；添加……