Niche Partitioning with Temperature among Heterocystous Cyanobacteria (Scytonema spp., Nostoc spp., and Tolypothrix spp.) from Biological Soil Crusts

Abstract

Heterocystous cyanobacteria of biocrusts are key players for biological fixation in drylands, where nitrogen is only second to water as a limiting resource. We studied the niche partitioning among the three most common biocrust heterocystous cyanobacteria sts using enrichment cultivation and the determination of growth responses to temperature in 30 representative isolates. Isolates of Scytonema spp. were most thermotolerant, typically growing up to 40 °C, whereas only those of Tolypothrix spp. grew at 4 °C. Nostoc spp. strains responded well at intermediate temperatures. We could trace the heat sensitivity in Nostoc spp. and Tolypothrix spp. to N2-fixation itself, because the upper temperature for growth increased under nitrogen replete conditions. This may involve an inability to develop heterocysts (specialized N2-fixing cells) at high temperatures. We then used a meta-analysis of biocrust molecular surveys spanning four continents to test the relevance of this apparent niche partitioning in nature. Indeed, the geographic distribution of the three types was clearly constrained by the mean local temperature, particularly during the growth season. This allows us to predict a potential shift in dominance in many locales as a result of global warming, to the benefit of Scytonema spp. populations.

Coleofasciculaceae, a Monophyletic Home for the Microcoleus steenstrupii Complex and Other Desiccation‐tolerant Filamentous Cyanobacteria

“…1996), frequency and intensity of desiccation (Rothrock and Garcia‐Pichel 2005), and temperature (Giraldo‐Silva et al. 2020). Among these variables, the latter two seemed most relevant for the soil habitat and could be readily obtained from climate databases in order to define a niche by correlation with published molecular ecology studied.…”

“…Biomass growth yields at 15 d were determined also as a function of temperature, based on chlorophyll a (Chl a ) production (see below: Quantitative Chlorophyll a determination), as previously described (Giraldo‐Silva et al. 2020).…”

Editorial for the Special Issue: Advances in the Biology of Phototrophic Bacteria

“…This Special Issue highlights recent advances in these aspects. It includes results specifically on green sulfur bacteria (Chlorobi [3]), heliobacteria (Firmicutes [4]), Chloroflexi [5], Cyanobacteria [6,7] and phototrophic purple bacteria (Proteobacteria [8][9][10][11][12][13]). In addition, phylogenetic studies regarding photosynthesis and osmotic adaptation consider representatives of all of these phyla [14,15].…”

“…In addition, phylogenetic studies regarding photosynthesis and osmotic adaptation consider representatives of all of these phyla [14,15]. This Special Issue includes results on identification and genomic characterization of new isolates [9], the adaptation to specific ecological niches in regard to temperature [6], salinity [14] and pH [4]. It also considers aerobic phototrophic purple bacteria and the relations to oxygen and oxidative stress [8][9][10][11]13] as well as environmental interactions [5,7,12] and syntrophic relations [3].…”

“…Over evolutionary times, phototrophic bacteria that have conquered different ecological niches have given rise to the evolution of phylogenetic groups of species that are living today in these niches. This is depicted in specific ecological niches of phylogenetic distinct groups of phototrophic bacteria with examples of some heliobacteria in alkaline waters [4], of different groups of phototrophic purple bacteria adapted to marine and hypersaline habitats [14] and of certain genera of cyanobacteria with different temperature responses [6]. The last aspect was studied by comparison of temperature responses of 30 isolates of these genera and by a meta-analysis of 84 locations around the world [6] and revealed advantages of Tolypothrix strains at lower temperatures, Scytonema strains at higher temperatures and Nostoc strains at moderate temperatures [6].…”