A. Flamholz

ATCG nucleotide fluctuation of Deinococcus radiodurans radiation genes

The radiation resistance-repair genes in Deinococcus radiodurans (DR) and E-coli were analyzed in terms of the A, T, C, G nucleotide fluctuations. The studied genes were Rec-A, Rec-Q, and the unique DR PprA gene. In an ATCG sequence, each base was assigned a number equal to its atomic number. The resulting numerical sequence was the basis of the statistical analysis. Fractal analysis using the Higuchi method gave a fractal dimension increase of the Deinococcus radiodurans genes as compared to E-coli, which is comparable to the enhancement observed in the human HAR1 region (HAR1F gene) over that of the chimpanzee. Near neighbor fluctuation was also studied via the Black-Scholes model where the increment sequence was treated as a random walk series. The Deinococcus radiodurans radiation gene standard deviations were consistently higher than that of the E-coli deviations, and agree with the fractal analysis results. The sequence stacking interaction was studied using the published nucleotide-pair melting free energy values and Deinococcus radiodurans radiation genes were shown to possess larger negative free energies. The high sensitivity of the fractal dimension as a biomarker was tested with correlation analysis of the gamma ray dose versus fractal dimension, and the R square values were found to be above 0.9 (N=5). When compared with other nucleotide sequences such as the rRNA sequences, HAR1 and its chimpanzee counterpart, the higher fluctuation (correlated randomness) and larger negative free energy of a DR radiation gene suggested that a radiation resistance-repair sequence exhibited higher complexity. As the HAR1 nucleotide sequence complexity and its transcription activity of co-expressing cortex protein reelin supported a positive selection event in humans, a similar inference of positive selection of coding genes could be drawn for Deinococcus radiodurans when compared to E-coli. The origin of such a positive selection would be consistent with that of a Martian environment.

Marfan Syndrome Exon CpG Percentage and Fractal Dimension

The CpG di-nucleotide percentage and exon fractal dimension fluctuation were investigated with respect to the recently identified Marfan syndrome exons in the FBN1 gene. The CpG di-nucleotide percentage was found to rank high in exon 1 (9%), exon 44 (6.5%), exon 24 (5.3%) and exon 27 (4.8%). The most significant Marfan exon group was reported to be exon 24- 32. An exon nucleotide sequence can be expressed as a numerical sequence when each nucleotide is assigned its proton number. The resulting exon nucleotide numerical sequence could be investigated for its fractal dimension. The fractal dimension exhibited fluctuation across the 65 FBN1 exons and the values formed a Gaussian-like distribution (N = 65). The moving average fractal dimension was found to exhibit a broad peak around exons 24 to 32, consistent with the reported Marfan syndrome exon group.

Nucleotide fluctuation of RecA repair gene in Siberian permafrost Psychrobacter cryohalolentis K5

A nucleotide sequence can be expressed as a numerical sequence when each nucleotide is assigned its proton number. A resulting gene numerical sequence can be investigated for its fractal dimension in terms of evolution and chemical properties for comparative studies. We have investigated such nucleotide fluctuation in the RecA repair gene of Psychrobacter cryohalolentis K5, Psychrobacter arcticus 273-4, and Psychrobacter sp. PRwf-1. The fractal dimension was found to correlate with the genes operating temperature with the highest fractal dimension associated with P. cryohalolentis K5 living at the low temperatures found in Siberian permafrost. The CpG dinucleotide content was found to be about 5% for the three species of Psychrobacters, which is substantially lower than that of Deinococcus radiodurans at about 12%. The average nucleotide pair-wise free energy was found to be lowest for Psychrobacter sp. PRwf-1, the species with the lowest fractal dimension of the three, consistent with the recent finding that Psychrobacter sp. PRw-f1 has a temperature growth maximum of 15-20°C higher than P. arcticus 273-4 and P. cryohaloentis K5. The results suggest that microbial vitality in extreme environments is associated with fractal dimension as well as high CpG dinucleotide content, while the average nucleotide pair-wise free energy is related to the operating environment. Evidence that extreme temperature operation would impose constraints measurable by Shannon entropy is also discussed. A quantitative estimate of an entropy-based measure having the characteristics of a mechanical pressure shows that the Psychrobacter RecA sequence experiences lower pressure than that of the human HAR1 sequence.

Fractal Analysis of Filamentous Actin Fluorescent Speckle Microscope Patterns in Cell Migration

The fluorescent speckle microscope pattern of newt lung epithelial cell filamentous actin during migration was analyzed using the Higuchi fractal method. The public domain datasets of 2004 PNAS Vallotton et al. were studied. The time series data from time lapsed images exhibited similar fractal dimensions (about 1.68 to 1.82) for various cell regions. Computer simulation of random time series data suggested an average fractal dimension of about 2 with a standard deviation of about 0.027. Speckle trend removals revealed pulsation features which were further studied using a sinusoidal signal model commonly used in gene regulatory studies. Gaussian noise models mixed with sinusoidal signal were used to simulate the observed fractal dimensions. The extracted constraints could be interpreted as polymerization and control pathway related. The administration of contractility promotion drug calyculin-A resulted in an increase of the overall image fractal dimension, which is consistent with the loss of correlation due to random direction contractions. It appears that high fractal dimension could be interpreted as being due to further randomization. Two doses of 20 nM calyculin-A increased cell noise by about 45%. Extension of this proof-of-concept fractal analysis to clinical treatment was also discussed.

DNA sequence-based comparative studies between non-extremophile and extremophile organisms with implications in exobiology

We have characterized function related DNA sequences of various organisms using informatics techniques, including fractal dimension calculation, nucleotide and multi-nucleotide statistics, and sequence fluctuation analysis. Our analysis shows trends which differentiate extremophile from non-extremophile organisms, which could be reproduced in extraterrestrial life. Among the systems studied are radiation repair genes, genes involved in thermal shocks, and genes involved in drug resistance. We also evaluate sequence level changes that have occurred during short term evolution (several thousand generations) under extreme conditions.

Fractal Analysis of Creutzfeld-Jakob Disease Frontal Horn Brain Magnetic Resonance Image

The Higuchi fractal method on a random series was applied to the study of the brightness fluctuation of Creutzfeld-Jakob disease (CJD) brain magnetic resonance (MR) frontal horn images. The brightness fluctuation along either a horizontal or vertical direction across an image formed a random series suitable for the Higuchi method. The average fractal dimension was found to decrease for the CJD frontal horn images (1.95) when compared to normal frontal horn images (1.97). The t-test gave a probability of about 7% that the CJD fractal dimension values would be a subset of a normal frontal horn dataset. Another MRI dataset taken later was also analyzed. The fractal dimension had increased to be about 1.99. Since the theoretical maximum fractal dimension for a line object is 2, a one-tailed t- test was used. The probability that the near expiration fractal dimension values coming from sampling from a normal dataset is about 15%. Extension to Parkinson MR images is discussed. The Higuchi fractal method could be used as a supplemental tool for extracting additional information and progress monitoring.

Multi-fractal property of perchlorate reductase gene sequences and DNA photonics application to UV fluorescence detection on Mars-like surfaces

The discovery of perchlorate on Mars raises the possibility of the existence of perchlorate reduction microbes on that planet. The perchlorate reductase gene sequence fractal dimensions of two Dechloromonas species were compared with five other sequences in the microbial dimethyl sulfoxide (DMSO) reductase family. A nucleotide sequence can be expressed as a numerical sequence where each nucleotide is assigned its proton number. The resulting numerical sequence can be investigated for its fractal dimension in terms of evolution and chemical properties for comparative studies. Analysis of the fractal dimensions for the DMSO reductase family supports phylogenetic analyses that show that the perchlorate reductase gene sequences are members of the same family. A sub-family with roughly the same nucleotide length emerges having the property that the gene fractal dimension is negatively correlated with the Shannon di-nucleotide entropy (R2 ~ 0.95, N =5). The gene sequence fractal dimension is found to be positively correlated with the neighbor joining distances reported in a published protein phylogeny tree (R2~ 0.92, N = 5). The multi-fractal property associated with these genes shows that perchlorate reductase has lower dimensionality as compared to the relatively higher dimensionality DNA-break repair genes Rec-A and Rad-A observed in the Dechloromonas aromatica and Deinococcus radiodurans genomes. The studied perchlorate gene sequences show a higher Shannon di-nucleotide entropy (~3.97 bits) relative to Dechloromonas aromatica DNA repair sequences (~3.87 bits Rec-A, ~3.92 bits Rad-A), suggesting that there are fewer constraints on nucleotide variety in the perchorlate sequences . These observations thus allow for the existence of perchlorate reducing microbes on Mars now or in the past. Timeresolved UV fluorescence study near the emission bands of nucleotide sequences could be used for bio-detection on Mars-like surfaces and the results may further constrain the proposed conjectures.

Nucleotide fluctuation of radiation-resistant Halobacterium sp. NRC-1 single-stranded DNA-binding protein (RPA) genes

The Single-Stranded DNA-Binding Protein (RPA) Genes in gamma ray radiation-resistant halophilic archaeon Halobacterium sp. NRC-1 were analyzed in terms of their nucleotide fluctuations. In an ATCG sequence, each base was assigned a number equal to its atomic number. The resulting numerical sequence was the basis of the statistical analysis in this study. Fractal analysis using the Higuchi method gave fractal dimensions of 2.04 and 2.06 for the gene sequences VNG2160 and VNG2162, respectively. The 16S rRNA sequence has a fractal dimension of 1.99. The di-nucleotide Shannon entropy values were found to be negatively correlated with the observed fractal dimensions (R2~ 0.992, N=3). Inclusion of Deinococcus radiodurans Rad-A in the regression analysis decreases the R2 slightly to 0.98 (N=4). A third VNG2163 RPA gene of unknown function but with upregulation activity under irradiation was found to have a fractal dimension of 2.05 and a Shannon entropy of 3.77 bits. The above results are similar to those found in bacterial Deinococcus radiodurans and suggest that their high radiation resistance property would have favored selection of CG di-nucleotide pairs. The two transcription factors TbpD (VNG7114) and TfbA (VNG 2184) were also studied. Using VNG7114, VNG2184, and VNG2163; the regression analysis of fractal dimension versus Shannon entropy shows that R2 ~ 0.997 for N =3. The VNG2163 unknown function may be related to the pathways with transcriptions closely regulated to sequences VNG7114 and VNG2184.

C2H2 Zinc Finger Nucleotide Fluctuation

A C2H2 zinc finger nucleotide sequence can be expressed as a numerical sequence when each nucleotide is assigned its proton number. A resulting zinc finger numerical sequence could be investigated for its fractal dimension in terms of evolution, multiple finger structure flexibility, and 3-finger structure specificity. The ZNF714 sequence was found to have a fractal dimension higher than its evolutionary ancestor ZNF431, consistent with the recently reported evolutionary direction using traditional analysis. The ZNF91 sequence has 36 zinc fingers and their fractal dimensions form a Gaussian-like histogram, suggesting a maximal flexibility for capacity dimension. The CpG di-nucleotide percentage in the three zinc fingers of EGR1 is found to correlate with the fractal dimension while the five zinc fingers in ZFP91 separated into human-chimp and mouse-rat-dog groups. Extension of the fractal investigation to short genetic sequences is discussed.

Phaeodactylum tricornutum photosynthesis and Thalassiosira pseudonana bio-silica formation genes nucleotide fluctuations

Diatom bioactivity has been reported to be responsible for about 20% of carbon fixation globally and together with other photosynthetic organisms, the bioactivity can be monitored via satellite ocean imaging. The bioinformatics embedded in the nucleotide fluctuations of photosynthesis and bio-silicate genes in diatoms were studied. The recently reported phosphoenolpyruvate carboxylase PEPC1 and PEPC2 C4-like photosynthesis genes in Phaeodactylum tricornutum were found to have similar fractal dimensions of about 2.01. In comparison, the green alga Chlamydomonas reinhardtii PEPC1 and PEPC2 genes have fractal dimensions of about 2.05. The PEPC CpG dinucleotide content is 8% in P. tricornutum and 10% in C. reinhardtii. Further comparison of the cell wall protein gene showed that the VSP1 gene sequence in C. reinhardtii has a fractal dimension of 2.03 and the bio-silica formation silaffin gene in Thalassiosira pseudonana has a fractal dimension of 2.01. The phosphoenolpyruvate carboxylase PPC1 and PPC2 in T. pseudonana were found to have fractal dimensions and CpG dinucleotide content similar to that of P. tricornutum. The fractal dimension of the dnaB replication helicase gene is about 1.98 for both diatoms as well as for the alga Heterosigma akashiwo. In comparison, the E. coli dnaB gene has a fractal dimension of about 2.03. Given that high fractal dimension and CpG dinucleotide content sequences have been associated with the presence of selective pressures, the relatively low fractal dimension gene sequences of the two unique properties of Earth-bound diatoms (photosynthesis and bio-silica cell wall) suggests the potential for the development of high fractal dimension sequences for adaptation in harsh environments.