The DNA of Bacteria of the World Ocean and the Earth in Cosmic Dust at the International Space Station

Abstract

Cosmic dust samples from the surface of the illuminator of the International Space Station (ISS) were collected by a crew member during his spacewalk. The sampler with tampon in a vacuum container was delivered to the Earth. Washouts from the tampon's material and the tampon itself were analyzed for the presence of bacterial DNA by the method of nested PCR with primers specific to DNA of the genus Mycobacteria, DNA of the strains of capsular bacteria Bacillus, and DNA encoding 16S ribosomal RNA. The results of amplification followed by sequencing and phylogenetic analysis indicated the presence of the bacteria of the genus Mycobacteria and the extreme bacterium of the genus Delftia in the samples of cosmic dust. It was shown that the DNA sequence of one of the bacteria of the genus Mycobacteria was genetically similar to that previously observed in superficial micro layer at the Barents and Kara seas' coastal zones. The presence of the wild land and marine bacteria DNA on the ISS suggests their possible transfer from the stratosphere into the ionosphere with the ascending branch of the global electric circuit. Alternatively, the wild land and marine bacteria as well as the ISS bacteria may all have an ultimate space origin.

Figure 1

The process of sampling with sampler “TEST.” Astronaut holds the body of sampler “TEST” in his left hand and the tampon holder screwed out in the open space in the right hand.

Figure 2

The process of the sampler “TEST” opening in the lab in a laminar flow hood with protection degree II. Room where the sample was processed had been pretreated with UV for 24 hours.

Figure 3

The results of amplification of nucleic acids extracted from the samples using universal primers specific for the 16S rRNA gene. Lane 1: tampon number 1, 2: washout from the cavity number 1, 3: membrane of tampon number 2, 4: washout from the tampon number 2, 5: membrane of washout number 2, 6: washout from the cavity number 2, 7: membrane of washout number 1, 8: tampon number 2, 9: tampon number 2, 10: membrane of tampon number 1, 11: negative control (PCR k−). Molecular weight markers (step 100 bp.) are applied on the last lane.

Figure 4

Phylogenetic dendrogram on the basis of the gene fragment obtained with universal primers specific to the Mycobacteria sp. DNA, Cosmos Seq # 1: the nucleotide sequence of a PCR product from the space dust. ML Seq # 2–ML Seq # 6: the nucleotide sequences of PCR products from the samples of sea surface microlayer.

Figure 5

Possible ways of intact DNA (bacterial forms) transfer to the orbit of the ISS and from ISS surface. Kinetic constants of different transfer pathways of microorganisms are indicated as follows: k_A: hypothetic Arrhenius' way from the interplanetary space, k_mt: possible mass transfer of the dispersed matter from the Earth surface to the ISS orbit with the ascending branch of the global electric circuit, k_ISS: possible contamination way from ISS internal volume to ISS surface, and k_d: dissipation of the dust from the ISS surface to space.

Box 1

The sequence of the DNA fragment (size 803 bp.) obtained by amplification of samples from ISS surface with universal primers specific to the bacterial 16S rRNA gene.

Box 2

Nucleotide sequence of a PCR fragment obtained by amplification of space dust with universal primers specific to gene of Mycobacteria sp.