Chapter 2: What Is Life?

The question "What is life?" has existed since the beginning of recorded history. However, the scientific and philosophical contexts of this question have changed and been refined as advancements in technology have revealed both fine details and broad connections in the network of life on Earth. Understanding the framework of the question "What is life?" is central to formulating other questions such as "Where else could life be?" and "How do we search for life elsewhere?" While many of these questions are addressed throughout the Astrobiology Primer 3.

Chapter 5: Major Biological Innovations in the History of Life on Earth.

All organisms living on Earth descended from a single, common ancestral population of cells, known as LUCA-the last universal common ancestor. Since its emergence, the diversity and complexity of life have increased dramatically. This chapter focuses on four key biological innovations throughout Earth's history that had a significant impact on the expansion of phylogenetic diversity, organismal complexity, and ecospace habitation.

Chapter 1: The Astrobiology Primer 3.0.

The Astrobiology Primer 3.0 (ABP3.0) is a concise introduction to the field of astrobiology for students and others who are new to the field of astrobiology.

Microbial helpers allow cyanobacteria to thrive in ferruginous waters.

The Great Oxidation Event (GOE) was a rapid accumulation of oxygen in the atmosphere as a result of the photosynthetic activity of cyanobacteria. This accumulation reflected the pervasiveness of O on the planet's surface, indicating that cyanobacteria had become ecologically successful in Archean oceans. Micromolar concentrations of Fe in Archean oceans would have reacted with hydrogen peroxide, a byproduct of oxygenic photosynthesis, to produce hydroxyl radicals, which cause cellular damage.

Novel insights into the taxonomic diversity and molecular mechanisms of bacterial Mn(III) reduction.

Soluble ligand-bound Mn(III) can support anaerobic microbial respiration in diverse aquatic environments. Thus far, Mn(III) reduction has only been associated with certain Gammaproteobacteria. Here, we characterized microbial communities enriched from Mn-replete sediments of Lake Matano, Indonesia.

Whole-genome sequencing reveals that Shewanella haliotis Kim et al. 2007 can be considered a later heterotypic synonym of Shewanella algae Simidu et al. 1990.

Previously, experimental DNA-DNA hybridization (DDH) between Shewanellahaliotis JCM 14758 and Shewanellaalgae JCM 21037 had suggested that the two strains could be considered different species, despite minimal phenotypic differences. The recent isolation of Shewanella sp. MN-01, with 99 % 16S rRNA gene identity to S.

Microbial manganese(III) reduction fuelled by anaerobic acetate oxidation.

Soluble manganese in the intermediate +III oxidation state (Mn ) is a newly identified oxidant in anoxic environments, whereas acetate is a naturally abundant substrate that fuels microbial activity. Microbial populations coupling anaerobic acetate oxidation to Mn reduction, however, have yet to be identified. We isolated a Shewanella strain capable of oxidizing acetate anaerobically with Mn as the electron acceptor, and confirmed this phenotype in other strains.

Uncovering Barriers to Teaching Assistants (TAs) Implementing Inquiry Teaching: Inconsistent Facilitation Techniques, Student Resistance, and Reluctance to Share Control over Learning with Students.

Inquiry-based teaching approaches are increasingly being adopted in biology laboratories. Yet teaching assistants (TAs), often novice teachers, teach the majority of laboratory courses in US research universities. This study analyzed the perspectives of TAs and their students and used classroom observations to uncover challenges faced by TAs during their first year of inquiry-based teaching.

Electron transport and protein secretion pathways involved in Mn(III) reduction by Shewanella oneidensis.

Soluble Mn(III) represents an important yet overlooked oxidant in marine and freshwater systems. The molecular mechanism of microbial Mn(III) reduction, however, has yet to be elucidated. Extracellular reduction of insoluble Mn(IV) and Fe(III) oxides by the metal-reducing γ-proteobacterium Shewanella oneidensis involves inner (CymA) and outer (OmcA) membrane-associated c-type cytochromes, the extracellular electron conduit MtrCAB, and GspD, the secretin of type II protein secretion.