Cytochrome Oxidase: Subcellular Distribution and Relationship to Nitrogenase Expression in the Nonheterocystous Marine Cyanobacterium Trichodesmium thiebautii

Abstract

Immunochemical labeling was used to study the subcellular distribution of cytochrome oxidase, a respiratory protein, in Trichodesmium thiebautii. The protein was found associated with both cytoplasmic and thylakoid membranes. About a sixfold variation in the protein content (gold particle count) was found among Trichodesmium cells within a single colony. Double labeling was performed with cytochrome oxidase and nitrogenase antisera. Regression analysis of gold particle counts per unit of cell area of cytochrome oxidase and nitrogenase showed a positive correlation (r2 = 0.911); cells with higher nitrogenase levels also had higher levels of cytochrome oxidase. The parallel expression of two proteins suggests that respiratory oxygen uptake may be involved in nitrogenase protection (respiratory protection) in Trichodesmium spp.

Iron requirements for dinitrogen‐ and ammonium‐supported growth in cultures of Trichodesmium (IMS 101): Comparison with nitrogen fixation rates and iron: carbon ratios of field populations

“…Nitrogenase activity is readily inhibited by molecular oxygen, and high rates of respiration may be needed to prevent oxygen toxicity. This is a common strategy for nonheterocystous daytime N 2 fixers (Gallon 1992) and is suggested in Trichodesmium by the colocalization of cytochrome oxidase and nitrogenase among cells within colonies in this genus (Bergman et al 1993). Iron-containing antioxidant enzymes may protect nitrogenase from reactive oxygen species, as suggested by Puppo and Rigaud (1986), and, therefore, may also contribute to an elevated diazotrophic iron cost.…”

N2 fixation in free‐floating filaments of Trichodesmium is higher than in transiently suboxic colony microenvironments

“…Our model calculations revealed that single cells can achieve anoxic conditions in the center with a cell wall permeability for O 2 between 2.6 9 10 À6 and 4.9 9 10 À6 m s À1 if they perform dark respiration at the average rate observed in this study (homogenous respiration, Table 3). Based on a previous study demonstrating single-cell variation in cytochrome oxidase content that was correlated to nitrogenase content in Trichodesmium thiebautii (Bergman et al, 1993), we also considered the effects of a six-fold higher respiration rate in diazocytes compared with vegetative cells, yielding somewhat higher permeability estimates between 1.6 9 10 À5 m s À1 and 3.1 9 10 À5 m s À1 (heterogeneous respiration, Table 3). These estimates exceed a previous one for Table 3 Calculated permeability of the cell wall necessary to support anoxia in the interior of a Trichodesmium cell, based on measured rates of O 2 uptake (that is, dark respiration), extracellular O 2 concentrations in colonies and cell dimensions (average 5 lm length, 7 lm width).…”

Trichodesmium– a widespread marine cyanobacterium with unusual nitrogen fixation properties

“…The increase in Mehler reaction (Kana, 1993;Milligan et al, 2007) and dark respiratory activity during the The diazotrophic physiology of Trichodesmium diazotrophic periods (Carpenter & Roenneberg, 1995;Kranz et al, 2009) is supported by the enhanced levels of the respiratory enzyme cytochrome c oxidase detected using proteomic analyses on N 2 -fixing cultures of Trichodesmium IMS101 (Sandh et al, 2011) and the enhanced levels of this enzyme specifically in the diazocytes, detected using immunogold localization in natural Trichodesmium populations (Bergman et al, 1993). In addition, Bryceson & Fay (1981) described zones of cells with higher tetrazolium salt depositions within specific areas of the trichomes, which support a reducing environment within the diazocytes.…”