information about changes in the catchment and land use and in the atmosphere and
are very sensitive to environmental and global changes (Adrian et al. 2009), mainly
remote depositions and global warming. These changes may induce rapid changes
in the microbial community composition and potentially erode the most idiosyncratic populations leading to species decline by ecosystem degradation.
Experimental evidence is however needed to test these hypotheses. New approaches
to predict the impacts of global change at the microbial community level are also
required for scientifically informed conservation and management of biodiversity
and ecosystem services (Bellard et al. 2012).
7.2 A Biodiversity Unit for the Microbial World
Systematics and taxonomy are fundamental tools to track biological history understanding life forms origins and relationships and to help to organise biological
complexity knowledge to support biological conservation, respectively (Cotterill
1995). Estimating the number of microbial species even at the order of magnitude is,
however, a great challenge in biology and matter of intense debate in microbiology.
Two of the main problems microbiologists have to successfully face this challenge
are the own definition of the species concept and the little success bringing into a
culture most of the wild microbes, respectively (Fig. 7.1). The species definition for
bacteria requires individuals previously isolated and grown in culture and needs
highly standardised laboratory protocols, comparative genomic information and a
dataset of physiological and other phenotypical features. Thus, a pragmatic phylophenetic species concept for microbial taxonomists is only useful if pure cultures
are available in the laboratory (Rosselló-Mora and Amann 2001). Currently, c. 13,000
bacterial and archaeal species are available in culture (Amann and Rosselló-Móra
2016). The last estimation using >20,000 microbial molecular surveys and mathematical modeling and scaling laws predicts the existence of between 10
11
–10
12
microbial species on Earth (Locey and Lennon 2016). If true, and according to the
current number of catalogued microorganisms, that would mean that 99.999% of total
microbial species are missing still. However, the lack of consensus ranges of several
orders of magnitude. Estimations based on the empirical analysis of the bacterial and
archaeal 16S rRNA gene sequences available in curated databases (c. 1.5 million
full-length sequences), reduce the molecular census to a few millions Operational
Taxonomic Units (OTU, 97% sequence identity “species-level” cutoff) (Schloss et al.
2016). In addition, it has also been predicted that environmental 16S rRNA gene
sequences of the highest novelty are reaching a plateau and that most of the high
microbial taxa will be discovered within a few years (Yarza et al. 2014). Still, to carry
out the inventory and interpretation of the most abundant organisms on earth is a vast
enterprise that will keep microbiologists busy for many decades. Telling apart
microbial species is still highly controversial and difficult, and a consensus definition
7 Towards a Microbial Conservation Perspective …
161
are very sensitive to environmental and global changes (Adrian et al. 2009), mainly
remote depositions and global warming. These changes may induce rapid changes
in the microbial community composition and potentially erode the most idiosyncratic populations leading to species decline by ecosystem degradation.
Experimental evidence is however needed to test these hypotheses. New approaches
to predict the impacts of global change at the microbial community level are also
required for scientifically informed conservation and management of biodiversity
and ecosystem services (Bellard et al. 2012).
7.2 A Biodiversity Unit for the Microbial World
Systematics and taxonomy are fundamental tools to track biological history understanding life forms origins and relationships and to help to organise biological
complexity knowledge to support biological conservation, respectively (Cotterill
1995). Estimating the number of microbial species even at the order of magnitude is,
however, a great challenge in biology and matter of intense debate in microbiology.
Two of the main problems microbiologists have to successfully face this challenge
are the own definition of the species concept and the little success bringing into a
culture most of the wild microbes, respectively (Fig. 7.1). The species definition for
bacteria requires individuals previously isolated and grown in culture and needs
highly standardised laboratory protocols, comparative genomic information and a
dataset of physiological and other phenotypical features. Thus, a pragmatic phylophenetic species concept for microbial taxonomists is only useful if pure cultures
are available in the laboratory (Rosselló-Mora and Amann 2001). Currently, c. 13,000
bacterial and archaeal species are available in culture (Amann and Rosselló-Móra
2016). The last estimation using >20,000 microbial molecular surveys and mathematical modeling and scaling laws predicts the existence of between 10
11
–10
12
microbial species on Earth (Locey and Lennon 2016). If true, and according to the
current number of catalogued microorganisms, that would mean that 99.999% of total
microbial species are missing still. However, the lack of consensus ranges of several
orders of magnitude. Estimations based on the empirical analysis of the bacterial and
archaeal 16S rRNA gene sequences available in curated databases (c. 1.5 million
full-length sequences), reduce the molecular census to a few millions Operational
Taxonomic Units (OTU, 97% sequence identity “species-level” cutoff) (Schloss et al.
2016). In addition, it has also been predicted that environmental 16S rRNA gene
sequences of the highest novelty are reaching a plateau and that most of the high
microbial taxa will be discovered within a few years (Yarza et al. 2014). Still, to carry
out the inventory and interpretation of the most abundant organisms on earth is a vast
enterprise that will keep microbiologists busy for many decades. Telling apart
microbial species is still highly controversial and difficult, and a consensus definition
7 Towards a Microbial Conservation Perspective …
161