Actinobacteria and Cyanobacteria Diversity in Terrestrial Antarctic Microenvironments Evaluated by Culture-Dependent and Independent Methods

Abstract

Bacterial diversity from McMurdo Dry Valleys in Antarctica, the coldest desert on earth, has become more easily assessed with the development of High Throughput Sequencing (HTS) techniques. However, some of the diversity remains inaccessible by the power of sequencing. In this study, we combine cultivation and HTS techniques to survey actinobacteria and cyanobacteria diversity along different soil and endolithic micro-environments of Victoria Valley in McMurdo Dry Valleys. Our results demonstrate that the Dry Valleys actinobacteria and cyanobacteria distribution is driven by environmental forces, in particular the effect of water availability and endolithic environments clearly conditioned the distribution of those communities. Data derived from HTS show that the percentage of cyanobacteria decreases from about 20% in the sample closest to the water source to negligible values on the last three samples of the transect with less water availability. Inversely, actinobacteria relative abundance increases from about 20% in wet soils to over 50% in the driest samples. Over 30% of the total HTS data set was composed of actinobacterial strains, mainly distributed by 5 families: Sporichthyaceae , Euzebyaceae , Patulibacteraceae , Nocardioidaceae , and Rubrobacteraceae . However, the 11 actinobacterial strains isolated in this study, belonged to Micrococcaceae and Dermacoccaceae families that were underrepresented in the HTS data set. A total of 10 cyanobacterial strains from the order Synechococcales were also isolated, distributed by 4 different genera ( Nodosilinea , Leptolyngbya , Pectolyngbya , and Acaryochloris -like). In agreement with the cultivation results, Leptolyngbya was identified as dominant genus in the HTS data set. Acaryochloris -like cyanobacteria were found exclusively in the endolithic sample and represented 44% of the total 16S rRNA sequences, although despite our efforts we were not able to properly isolate any strain from this Acaryochloris -related group. The importance of combining cultivation and sequencing techniques is highlighted, as we have shown that culture-dependent methods employed in this study were able to retrieve actinobacteria and cyanobacteria taxa that were not detected in HTS data set, suggesting that the combination of both strategies can be usefull to recover both abundant and rare members of the communities.

Diversity of Bacterial Biosynthetic Genes in Maritime Antarctica

“…In agreement, the principal components analysis (PCA) applied to the environmental variables (Table S1) indicates that sample 54 was distinguished from others by being associated with high total organic matter and water content ( Figure S2). A previous study from our team [47] has revealed that in samples with higher water availability, from McMurdo Dry Vallleys, Antarctica, Actinobacteria dominance was replaced by other phyla, such as Cyanobacteria. Similarly, sample 54 harbors a lower relative abundance and richness of Actinobacteria ( Figure 4A) which might be related to the observed shift in KS/AD diversity ( Figure 2).…”

Energetic Basis of Microbial Growth and Persistence in Desert Ecosystems

“…Trace gas oxidation may explain why Actinobacteria is the dominant bacterial phylum in desert soils. The relative abundance of this phylum increases with aridity (147,148), and it typically accounts for 30 to 80% of the microbial community in hyper-arid sites (7,13,132,145,147,149) (Fig. 1).…”

The Extremophile Endolithella mcmurdoensis gen. et sp. nov. (Trebouxiophyceae, Chlorellaceae), A New Chlorella‐like Endolithic Alga From Antarctica

“…Isolate LEGE Z‐009 was obtained from an isolation process originally intended for isolating cyanobacteria (Rego et al. ). An aliquot of the endolithic sample was washed and centrifuged three times (4500 g , 3 min) with nitrogen‐free BG11 0 medium (Rippka ).…”