active drifting in atmospheric clouds, and every time that one of us inhales a breath
of fog we also are inhaling a countlessly high number of respiring microbes.
Microbial persistence in the freezer-burned surface soils of Antarctica sometimes
means obtaining liquid water by surviving hypersaline conditions within the soils’
interstitial pores. Lithotrophic microbes may play the less charismatic roles in
microbiology, but their reliance on alternative electron acceptors allows the
lithotrophs to provide a foundation for the world’s deep subsurface ecosystems.
The third section presents our “Understanding the core values of microbial
metabolism.” Life, as we know it on this planet, has a very critical need for
nitrogen’s presence in proteins. The occurrence of nitrogen in its different oxidation
states also has an important role in numerous cycles which provide energy for
microorganisms. Oxidation of methane provides energy in anaerobic environments
when coupled with various terminal electron acceptors such as metals, nitrogen
compounds, and sulfate. Within marine sediments, microbes can couple the oxidation of sulfide in anaerobic layers with a near simultaneous reduction of the oxygen
present in overlying aerobic layers. Anoxygenic photosynthesis by bacteriochlorophyll can oxidize hydrogen sulfide to release sulfur, and evolutionarily that process
may well have preceded the oxygenic photosynthesis which created our oxygen-rich
atmosphere by oxidizing water molecules.
The fourth section examines some aspects of how “Microbes established and
sustain life.” There is a duality in the microbial world; its various processes include
some that we perceive as being environmentally good and contributing toward longterm ecological stability, although other processes seem environmentally destructive. Very often, we notice only the large-scale results and seem to ignore that all
large-scale microbial processes are the sum of microscale activity.
Human activities unintentionally enhance some of the environmentally destructive microbial processes that contribute to climate change, including the
overproduction of greenhouse gasses such as carbon dioxide, methane, and nitrous
oxide, which increase the warming of our atmosphere. The warming of our atmosphere does in turn destructively increase the warming of our oceans. We need to
work on improving the environmentally beneficial side of that microbial duality. The
future of our biosphere depends in part upon aquatic carbon cycles including those
which occur in the ocean. Looking toward the goal of achieving environmentally
supportive microbial activity on the land, cultivating beneficial microbial communities by means of regenerative farming systems may help to mitigate damage that is
caused by agriculture’s environmental footprint. It is possible that modification of
agricultural processes can reduce greenhouse gas emissions and ultimately increase
carbon sequestration. Changing human dietary practices can cultivate beneficial gut
microbiomes. The functions of a forest, and the functions of agricultural fields,
depend upon the microbial functions within their soil. The functions of aquatic
ecosystems similarly depend upon the activities of their microbial communities.
The fifth section reveals our knowledge regarding “The basic aspects of microbial
symbioses.” Our efforts to understand the symbiotic nature of microbial life can be
traced back to Mikhail Stepanovich Voronin’s conclusion, published in 1866, that
the nodular root growths on black alder (Alnus glutinosa), and the bulbous root
Volume Preface
xv
of fog we also are inhaling a countlessly high number of respiring microbes.
Microbial persistence in the freezer-burned surface soils of Antarctica sometimes
means obtaining liquid water by surviving hypersaline conditions within the soils’
interstitial pores. Lithotrophic microbes may play the less charismatic roles in
microbiology, but their reliance on alternative electron acceptors allows the
lithotrophs to provide a foundation for the world’s deep subsurface ecosystems.
The third section presents our “Understanding the core values of microbial
metabolism.” Life, as we know it on this planet, has a very critical need for
nitrogen’s presence in proteins. The occurrence of nitrogen in its different oxidation
states also has an important role in numerous cycles which provide energy for
microorganisms. Oxidation of methane provides energy in anaerobic environments
when coupled with various terminal electron acceptors such as metals, nitrogen
compounds, and sulfate. Within marine sediments, microbes can couple the oxidation of sulfide in anaerobic layers with a near simultaneous reduction of the oxygen
present in overlying aerobic layers. Anoxygenic photosynthesis by bacteriochlorophyll can oxidize hydrogen sulfide to release sulfur, and evolutionarily that process
may well have preceded the oxygenic photosynthesis which created our oxygen-rich
atmosphere by oxidizing water molecules.
The fourth section examines some aspects of how “Microbes established and
sustain life.” There is a duality in the microbial world; its various processes include
some that we perceive as being environmentally good and contributing toward longterm ecological stability, although other processes seem environmentally destructive. Very often, we notice only the large-scale results and seem to ignore that all
large-scale microbial processes are the sum of microscale activity.
Human activities unintentionally enhance some of the environmentally destructive microbial processes that contribute to climate change, including the
overproduction of greenhouse gasses such as carbon dioxide, methane, and nitrous
oxide, which increase the warming of our atmosphere. The warming of our atmosphere does in turn destructively increase the warming of our oceans. We need to
work on improving the environmentally beneficial side of that microbial duality. The
future of our biosphere depends in part upon aquatic carbon cycles including those
which occur in the ocean. Looking toward the goal of achieving environmentally
supportive microbial activity on the land, cultivating beneficial microbial communities by means of regenerative farming systems may help to mitigate damage that is
caused by agriculture’s environmental footprint. It is possible that modification of
agricultural processes can reduce greenhouse gas emissions and ultimately increase
carbon sequestration. Changing human dietary practices can cultivate beneficial gut
microbiomes. The functions of a forest, and the functions of agricultural fields,
depend upon the microbial functions within their soil. The functions of aquatic
ecosystems similarly depend upon the activities of their microbial communities.
The fifth section reveals our knowledge regarding “The basic aspects of microbial
symbioses.” Our efforts to understand the symbiotic nature of microbial life can be
traced back to Mikhail Stepanovich Voronin’s conclusion, published in 1866, that
the nodular root growths on black alder (Alnus glutinosa), and the bulbous root
Volume Preface
xv