- Gunawardana D., Wanigatunge R.P., Wewalwela J.J., Vithanage M.M. & Wijeyaratne C.
- Acta Biotheoretica
- 71: 14 [20 p.]
Cyanolichens are symbiotic organisms involving cyanobacteria and fungi (bipartite)
or with the addition of an algal partner (tripartite). Cyanolichens are known for their
heightened susceptibility to environmental pollution. We focus here on the impacts
on cyanolichens due to rising air pollution; we are especially interested in the role of
sulfur dioxide on cyanolichen biology. Cyanolichens due to air pollution including
sulfur dioxide exposure, show symptomatic changes including degradation of
chlorophyll, lipid membrane peroxidation, decrease in ATP production, changes
in respiration rate, and alteration of endogenous auxins and ethylene production,
although symptoms are known to vary with species and genotype. Sulfur dioxide
has been shown to be damaging to photosynthesis but is relatively benign on
nitrogen fxation which proposes as a hypothesis that the algal partner may be
more in harm’s way than the cyanobiont. In fact, the Nostoc cyanobiont of sulfur
dioxide-susceptible Lobaria pulmonaria carries a magnified set of sulfur (alkane
sulfonate) metabolism genes capable of alkane sulfonate transport and assimilation,
which were only unraveled by genome sequencing, a technology unavailable in
the 1950–2000 epoch, where most physiology- based studies were performed.
There is worldwide a growing corpus of evidence that sulfur has an important
role to play in biological symbioses including rhizobia-legumes, mycorrhizae-roots and cyanobacteria-host plants. Furthermore, the fungal and algal partners of
L. pulmonaria appear not to have the sulfonate transporter genes again providing
the roles of ambient-sulfur (alkanesulfonate metabolism etc.) mediated functions
primarily to the cyanobacterial partner. In conclusion, we have addressed here the
role of the atmospheric pollutant sulfur dioxide to tripartite cyanolichen viability
and suggest that the weaker link is likely to be the photosynthetic algal (chlorophyte)
partner and not the nitrogen-fixing cyanobiont.
Keywords: Alkane sulfonate · Cyanobionts · Cyanolichens · Fungi · Lobaria
pulmonaria · Sulfur dioxide.
- Monday, 22 May 2023 22:57