Nitrogen fixation and nifH diversity in human gut microbiota
- Igai, Katsura, Itakura, Manabu, Nishijima, Suguru, Tsurumaru, Hirohito, Suda, Wataru, Tsutaya, Takumi, Tomitsuka, Eriko, Tadokoro, Kiyoshi, Baba, Jun, Odani, Shingo, Natsuhara, Kazumi, Morita, Ayako, Yoneda, Minoru, Greenhill, Andrew, Horwood, Paul, Inoue, Jun-ichi, Ohkuma, Moriya, Hongoh, Yuichi, Yamamoto, Taro, Siba, Peter, Hattori, Masahira, Minamisawa, Kiwamu, Umezaki, Masahiro
- Authors: Igai, Katsura , Itakura, Manabu , Nishijima, Suguru , Tsurumaru, Hirohito , Suda, Wataru , Tsutaya, Takumi , Tomitsuka, Eriko , Tadokoro, Kiyoshi , Baba, Jun , Odani, Shingo , Natsuhara, Kazumi , Morita, Ayako , Yoneda, Minoru , Greenhill, Andrew , Horwood, Paul , Inoue, Jun-ichi , Ohkuma, Moriya , Hongoh, Yuichi , Yamamoto, Taro , Siba, Peter , Hattori, Masahira , Minamisawa, Kiwamu , Umezaki, Masahiro
- Date: 2016
- Type: Text , Journal article
- Relation: Scientific Reports Vol. 6, no. (2016), p. 1-11
- Full Text:
- Reviewed:
- Description: It has been hypothesized that nitrogen fixation occurs in the human gut. However, whether the gut microbiota truly has this potential remains unclear. We investigated the nitrogen-fixing activity and diversity of the nitrogenase reductase (NifH) genes in the faecal microbiota of humans, focusing on Papua New Guinean and Japanese individuals with low to high habitual nitrogen intake. A 15 N 2 incorporation assay showed significant enrichment of 15 N in all faecal samples, irrespective of the host nitrogen intake, which was also supported by an acetylene reduction assay. The fixed nitrogen corresponded to 0.01% of the standard nitrogen requirement for humans, although our data implied that the contribution in the gut in vivo might be higher than this value. The nifH genes recovered in cloning and metagenomic analyses were classified in two clusters: one comprising sequences almost identical to Klebsiella sequences and the other related to sequences of Clostridiales members. These results are consistent with an analysis of databases of faecal metagenomes from other human populations. Collectively, the human gut microbiota has a potential for nitrogen fixation, which may be attributable to Klebsiella and Clostridiales strains, although no evidence was found that the nitrogen-fixing activity substantially contributes to the host nitrogen balance. © The Author(s) 2016.
- Authors: Igai, Katsura , Itakura, Manabu , Nishijima, Suguru , Tsurumaru, Hirohito , Suda, Wataru , Tsutaya, Takumi , Tomitsuka, Eriko , Tadokoro, Kiyoshi , Baba, Jun , Odani, Shingo , Natsuhara, Kazumi , Morita, Ayako , Yoneda, Minoru , Greenhill, Andrew , Horwood, Paul , Inoue, Jun-ichi , Ohkuma, Moriya , Hongoh, Yuichi , Yamamoto, Taro , Siba, Peter , Hattori, Masahira , Minamisawa, Kiwamu , Umezaki, Masahiro
- Date: 2016
- Type: Text , Journal article
- Relation: Scientific Reports Vol. 6, no. (2016), p. 1-11
- Full Text:
- Reviewed:
- Description: It has been hypothesized that nitrogen fixation occurs in the human gut. However, whether the gut microbiota truly has this potential remains unclear. We investigated the nitrogen-fixing activity and diversity of the nitrogenase reductase (NifH) genes in the faecal microbiota of humans, focusing on Papua New Guinean and Japanese individuals with low to high habitual nitrogen intake. A 15 N 2 incorporation assay showed significant enrichment of 15 N in all faecal samples, irrespective of the host nitrogen intake, which was also supported by an acetylene reduction assay. The fixed nitrogen corresponded to 0.01% of the standard nitrogen requirement for humans, although our data implied that the contribution in the gut in vivo might be higher than this value. The nifH genes recovered in cloning and metagenomic analyses were classified in two clusters: one comprising sequences almost identical to Klebsiella sequences and the other related to sequences of Clostridiales members. These results are consistent with an analysis of databases of faecal metagenomes from other human populations. Collectively, the human gut microbiota has a potential for nitrogen fixation, which may be attributable to Klebsiella and Clostridiales strains, although no evidence was found that the nitrogen-fixing activity substantially contributes to the host nitrogen balance. © The Author(s) 2016.
Coupling of cellular processes and their coordinated oscillations under continuous light in Cyanothece sp. ATCC 51142, a diazotrophic unicellular cyanobacterium
- Krishnakumar, Sujatha, Gaudana, Sandeep, Vinh, Nguyen, Viswanathan, Ganesh, Chetty, Madhu, Wangikar, Pramod
- Authors: Krishnakumar, Sujatha , Gaudana, Sandeep , Vinh, Nguyen , Viswanathan, Ganesh , Chetty, Madhu , Wangikar, Pramod
- Date: 2015
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 10, no. 5 (2015), p. 1-23
- Full Text:
- Reviewed:
- Description: Unicellular diazotrophic cyanobacteria such as Cyanothece sp. ATCC 51142 (henceforth Cyanothece), temporally separate the oxygen sensitive nitrogen fixation from oxygen evolving photosynthesis not only under diurnal cycles (LD) but also in continuous light (LL). However, recent reports demonstrate that the oscillations in LL occur with a shorter cycle time of ∼11 h. We find that indeed, majority of the genes oscillate in LL with this cycle time. Genes that are upregulated at a particular time of day under diurnal cycle also get upregulated at an equivalent metabolic phase under LL suggesting tight coupling of various cellular events with each other and with the cell's metabolic status. A number of metabolic processes get upregulated in a coordinated fashion during the respiratory phase under LL including glycogen degradation, glycolysis, oxidative pentose phosphate pathway, and tricarboxylic acid cycle. These precede nitrogen fixation apparently to ensure sufficient energy and anoxic environment needed for the nitrogenase enzyme. Photosynthetic phase sees upregulation of photosystem II, carbonate transport, carbon concentrating mechanism, RuBisCO, glycogen synthesis and light harvesting antenna pigment biosynthesis. In Synechococcus elongates PCC 7942, a non-nitrogen fixing cyanobacteria, expression of a relatively smaller fraction of genes oscillates under LL condition with the major periodicity being 24 h. In contrast, the entire cellular machinery of Cyanothece orchestrates coordinated oscillation in anticipation of the ensuing metabolic phase in both LD and LL. These results may have important implications in understanding the timing of various cellular events and in engineering cyanobacteria for biofuel production. © 2015 Krishnakumar et al.
- Authors: Krishnakumar, Sujatha , Gaudana, Sandeep , Vinh, Nguyen , Viswanathan, Ganesh , Chetty, Madhu , Wangikar, Pramod
- Date: 2015
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 10, no. 5 (2015), p. 1-23
- Full Text:
- Reviewed:
- Description: Unicellular diazotrophic cyanobacteria such as Cyanothece sp. ATCC 51142 (henceforth Cyanothece), temporally separate the oxygen sensitive nitrogen fixation from oxygen evolving photosynthesis not only under diurnal cycles (LD) but also in continuous light (LL). However, recent reports demonstrate that the oscillations in LL occur with a shorter cycle time of ∼11 h. We find that indeed, majority of the genes oscillate in LL with this cycle time. Genes that are upregulated at a particular time of day under diurnal cycle also get upregulated at an equivalent metabolic phase under LL suggesting tight coupling of various cellular events with each other and with the cell's metabolic status. A number of metabolic processes get upregulated in a coordinated fashion during the respiratory phase under LL including glycogen degradation, glycolysis, oxidative pentose phosphate pathway, and tricarboxylic acid cycle. These precede nitrogen fixation apparently to ensure sufficient energy and anoxic environment needed for the nitrogenase enzyme. Photosynthetic phase sees upregulation of photosystem II, carbonate transport, carbon concentrating mechanism, RuBisCO, glycogen synthesis and light harvesting antenna pigment biosynthesis. In Synechococcus elongates PCC 7942, a non-nitrogen fixing cyanobacteria, expression of a relatively smaller fraction of genes oscillates under LL condition with the major periodicity being 24 h. In contrast, the entire cellular machinery of Cyanothece orchestrates coordinated oscillation in anticipation of the ensuing metabolic phase in both LD and LL. These results may have important implications in understanding the timing of various cellular events and in engineering cyanobacteria for biofuel production. © 2015 Krishnakumar et al.
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