  The microbiome-gut-brain-axis field is multidisciplinary, benefiting from the
expertise of microbiology, ecology, psychiatry, computational biology, and
epidemiology amongst other disciplines. As the field matures and moves beyond a
basic demonstration of its relevance, it is critical that study design and
analysis are robust and foster reproducibility.
  In this companion piece to Bugs as Features (part I), we present techniques
from adjacent and disparate fields to enrich and inform the analysis of
microbiome-gut-brain-axis data. Emerging techniques built specifically for the
microbiome-gut-brain axis are also demonstrated. All of these methods are
contextualised to inform several common challenges: how do we establish
causality? How can we integrate data from multiple 'omics techniques? How might
we account for the dynamicism of host-microbiome interactions?
  This perspective is offered to experienced and emerging microbiome scientists
alike, to assist with these questions and others, at the study conception,
design, analysis and interpretation stages of research.
