Permanent Draft Genome Sequences for Two Variants of Frankia sp. Strain CpI1, the First Frankia Strain Isolated from Root Nodules of Comptonia peregrina

Frankia stains CpI1-S and CpI1-P are members of Frankia lineage Ia that are able to reinfect plants of the Betulaceae and Myricaceae families. Here, we report two 7.6-Mbp draft genome sequences with 6,396 and 6,373 candidate protein-coding genes for CpI1-S and CpI1-P, respectively.

Truncated hemoglobins in Frankia CcI3: effects of nitrogen source, oxygen concentration, and nitric oxide

Frankia strain CcI3 produces 2 truncated hemoglobins, HbN and HbO. Using ion-exchange chromatography, we characterized the expression of the relative amounts of HbN and HbO in −N (nitrogen-fixing) cultures and +N (nitrogen-supplemented) cultures. The −N cultures maintained an approximately constant ratio of HbO to HbN throughout the life of the culture, with HbO constituting 80%–85% of the total hemoglobin produced. In contrast, in +N cultures, HbN was observed to increase over time and HbO decreased. Total hemoglobin as a fraction of total protein was approximately constant throughout the growth phase in −N cultures, while it decreased somewhat in +N cultures. Subjecting −N cultures to a NO generator resulted in increased production of HbN, relative to the controls. Nitrite accumulated in +N cultures, but not in −N cultures. This suggests that the greater amount of HbN in +N cultures might be due to NO produced by the reduction of nitrite. The effects of O2 concentration were determined in +N cultures. Cultures grown in 1% O2 produced about 4 times more HbO than cultures grown in 20% O2. Overall, these results provide evidence for a role of HbN in NO oxidation and for a role of HbO in adaptation to low oxygen concentrations.

Nitric Oxide and Oxygen Regulate Truncated Hemoglobin Gene Expression in Frankia Strain CcI3

ABSTRACT The Frankia genome contains two truncated hemoglobin genes (hboN and hboO) whose functions remain to be determined. Nitric oxide (NO) generated by the addition of 400 μM SNAP (S-nitroso-N-acetylpenicillamine) caused a 10-fold increase in hboN gene expression but had no effect on hboO expression. The addition of the NO scavenger, carboxy-PT10, reduced the effect of SNAP. hboO gene expression increased under low-oxygen conditions, while hboN expression was unaffected. These results suggest that HboN may function in protection from nitrosative stress and that HboO may act as an oxygen transport molecule for increased respiration in hypoxic environments.