Microbial growth at hyperaccelerations up to 403,627 x g

Abstract

It is well known that prokaryotic life can withstand extremes of temperature, pH, pressure, and radiation. Little is known about the proliferation of prokaryotic life under conditions of hyperacceleration attributable to extreme gravity, however. We found that living organisms can be surprisingly proliferative during hyperacceleration. In tests reported here, a variety of microorganisms, including Gram-negative Escherichia coli, Paracoccus denitrificans, and Shewanella amazonensis; Gram-positive Lactobacillus delbrueckii; and eukaryotic Saccharomyces cerevisiae, were cultured while being subjected to hyperaccelerative conditions. We observed and quantified robust cellular growth in these cultures across a wide range of hyperacceleration values. Most notably, the organisms P. denitrificans and E. coli were able to proliferate even at 403,627 × g. Analysis shows that the small size of prokaryotic cells is essential for their proliferation under conditions of hyperacceleration. Our results indicate that microorganisms cannot only survive during hyperacceleration but can display such robust proliferative behavior that the habitability of extraterrestrial environments must not be limited by gravity.

Fig. 1.

Growth of P. denitrificans at 403,627 × g. Photographs of pellet of P. denitrificans cells after incubation at 403,627 × g and 30 °C for 0 h (A), 6 h (B), 24 h (C), and 48 h (D). The outer diameter of the tube is 18 mm.

Fig. 2.

Growth of various microorganisms under hyperaccelerations. (A) Growth curves of P. denitrificans at 30 °C and hyperaccelerations up to 403,627 × g. (B) Growth of E. coli in LB broth at 37 °C and hyperaccelerations up to 74,558 × g. (C) Growth of S. amazonensis in LB broth at 37 °C and hyperaccelerations up to 74,558 × g. (D) Growth of L. delbrueckii subsp. delbrueckii in MRS broth at 37 °C and hyperaccelerations up to 30,000 × g. (E) Growth of S. cerevisiae in yeast extract-peptone-dextrose broth at 30 °C and hyperaccelerations up to 74,558 × g. (F) Change in g_rel of various microorganisms as a function of acceleration.

Fig. 3.

Concentration gradient of model proteins within a cell. (A) Calculated concentration gradients of model proteins of different molecular masses (1 kDa, 10 kDa, 100 kDa, and 1 MDa) at the sedimentation equilibrium at 500,000 × g and 30 °C over a distance of 10 μm. (B) Sedimentation of model proteins of different molecular masses over a distance of 1 μm as a function of acceleration.

Fig. 4.

P. denitrificans cells after incubation at hyperaccelerations. Transmission electron microscopy images of P. denitrificans cells after incubation at 30 °C and at 1 × g for 4 h (A) and 134,425 × g for 48 h (B and C). (C) Occasionally, highly elongated cells were observed when incubated at 134,425 × g (white arrowhead). (Scale bar: 2 μm.) (D–F) Size distribution of P. denitrificans cells after incubation at 1 × g (black) and 134,425 × g (red).