Bioreactor Assembly for Continuous Culture of Complex Fecal Communities

Summary

This protocol details the assembly of mini-bioreactor arrays to be utilized for continuous flow culture of complex fecal communities under anaerobic conditions. We also discuss the methods for assembly, inoculation, and sampling of the reactors for further analysis.

Abstract

The microbiota, especially bacteria, respond to various environmental exposures such as micro and macronutrients, pharmacological compounds, and inflammatory mediators, which dynamically alter community composition and microbial metabolic output. Understanding how physiological culture conditions affect microbial communities and diversity and their metabolic capacity will contribute important knowledge of their impact on health and diseases. Here, we present a protocol adapted from the template published by Auchtung et al. to create mini-bioreactor arrays that can cultivate complex fecal communities, define bacterial consortiums or single strains under precise conditions, including nutrient availability, temperature, flow rate, pH, and oxygen content. We describe the process for building the mini-bioreactor system, including adaptations to improve limitations in the published protocol. We also discuss the setup of the mini-bioreactor system under anaerobic conditions with the use of MEGA media (adapted from Han et al.), which is a rich media supporting the growth of diverse bacteria. We describe the inoculation of gut humanized mouse fecal samples into the mini-bioreactor system, followed by the establishment of complex community cultures within the mini-bioreactor system, which can be grown under continuous flow with aseptic sampling to monitor community composition. This system is adaptable to dietary changes and other cultural modifications. The techniques described here allow for the characterization of diverse, fastidious fecal communities under dynamic conditions or in response to perturbation in isolation from host-derived factors.

Introduction

The gut microbiota is a vast network of microorganisms, including bacteria, fungi, archaea, and viruses, which contain a huge genetic and metabolic repertoire that greatly outnumbers that of a human host¹. The microbiome's rich metabolic capacity includes metabolites produced from bacterial processing of dietary nutrients, host metabolites chemically modified by bacteria, and metabolites synthesized uniquely by the microbiota². Microbiota is implicated in nearly all host bioprocesses but also in disease states like inflammatory bowel disease, cancer, metabolic disorders, and even neurological disorders^2....

Protocol

Fecal samples used in this study were obtained from experiments approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Florida (UF) and performed at UF Animal Care Facilities (IACUC Protocol #IACUC202300000005). Briefly, mixed gender germ-free wild-type (GF WT; C57BL/6) mice (bred and maintained in isolators by UF Animal Care Services Germ-free Division) were transferred from breeding isolators and placed into the ISOcage P Bioexclusion system to allow for microbial manipulation. Equal colony-forming units (CFU) from human donor feces were pooled for gavage into mice. Two weeks post-inoculation, fecal samples were collected from these....

Results

Fecal samples were collected from mice colonized with human fecal slurry 2 weeks post-inoculation and stored at -80 °C. The bioreactor system was set up with continuous MEGA media flow for two replicate reactor wells (Figure 3A). The fecal slurry was prepared from the mouse fecal pellets according to the protocol described in step 6, and both reactors were inoculated by sample port with the responder mouse fecal slurry. After overnight incubation of the fecal.......

Discussion

The mini-bioreactor system described in this protocol enables the cultivation of independent fecal communities for parallel experimentation. This ability to study microbial communities in isolation of host factors is an essential approach to understanding the intrinsic capacity of microorganisms to adapt to their environment. This protocol can be easily adapted for the cultivation of defined bacterial consortia or even single isolate cultures if desired. The MEGA media described here is a rich, anaerobic broth designed f.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1 mL BD Slip Tip Syringe sterile, single use	Fisher Scientific	309659
1/4-28 mm thread to barbed male adaptor (3.2 mm), 5/pack	Cole-Parmer	008NB32-KD5L	To build 1 6-well array, need 2 packs
10M NaOH (Sodium Hydroxide)	Sigma	72068-100ML
2.0ml Screw Cap Tube, NonKnurl, Skirted,Natural, E-Beam Sterile tube w/ attached cap	Fisher Scientific	14-755-228
2mag MIXdrive 60 Stirring Drive	2mag	40060	60-position magnetic stir plate (optional addition of heating capacity- cat# 40260)
6-well reactor arrray, ABS-Like Translucent Clear plastic	Protolabs	Custom	See supplementary files for .stl file for 3D printing
Absolute Ethanol (200 Proof)	Fisher Scientific	BP2818
Acetic acid, glacial	Sigma	A6283
Adapter, nylon, male luer to 1/4-28 thread, 25/pack	Cole-Parmer	EW-45505-82	To build 1 6-well array, need 6 (1 pack)
Aluminum foil	Fisher Scientific	01-213-100
Anaerobic chamber	Coy Lab Products	Type B
Bel-Art SP Scienceware Flea Micro Spinbar Magnetic Stirring Bars (1/pk)	Fisher Scientific	22-261679	To build 1 6-well array, need 6
Biosafety cabinet class 2	Nuaire
Butyric acid	Sigma	B103500
CaCl2 · 2H2O (Calcium Chloride Dihydrate)	Sigma	C7902
Clorox Healthcare Germicidal Wipes With Bleach, Unscented, 6" x 5", Pack Of 150 Wipes	Office Depot	129202
D-(-)-Fructose	Sigma	F0127-100G
D-(+)-Cellobiose	Sigma	C7252-100G
D-(+)-Glucose	Sigma	G8270-100G
D-(+)-Maltose monohydrate	Sigma	M5885-100G
Drill America Plug Hand Tap DWTP1/4-28	Home Depot	305699489
Dulbecco's Phosphate Buffered Saline, 1X without Ca and Mg, Sterile	Genesee	25-508
Female luer × 1/16″ hose barb adapter, Nylon, 25/pack	Cole-Parmer	EW-45502-00	To build 1 6-well array, need 24 (1 pack)
Female luer × 1/8″ hose barb adapter, Nylon 25/pack	Cole-Parmer	EW-45502-04	To build 1 6-well array, need 6 (1 pack)
Female luer × 3/32″ hose barb adapter, Nylon, 25/ pack	Cole-Parmer	EW-45502-02	To build 1 6-well array, need 6 (1 pack)
Female luer tee, Nylon, 25/pack	Cole-Parmer	EW-45502-56	To build 1 6-well array, need 10 (1 pack)
FeSO4 · 7H2O (Iron [II] Sulfate Heptahydrate)	Sigma	F8633
Hematin	Sigma	H3281
Histidine	Sigma	H7750
Isovaleric acid	Sigma	129542
K2HPO4 dibasic (dipotassium hydrogen phosphate)	Sigma	P2222-1KG
KH2PO4 monobasic (potassium dihydrogen phosphate)	Sigma	P0662-500G
Large Orifice Pipet Tips	Fisher Scientific	02-707-134
L-Cysteine hydrochloride	Sigma	C1276-10G
Male luer with lock ring × 1/8″ hose barb adapter, Nylon, 25/pack	Cole-Parmer	EW-45505-04	To build 1 6-well array, need 42 (2 packs)
Meat extract	Sigma	70164-500G
Med Vet International Exel Needle, 20G X 1", Hypodermic, 100/Box, 26417	Fisher Scientific	50-209-2532
Menadione (Vitamin K3)	Sigma	M5625
MgSO4 · 7H2O (Magnesium Sulfate Heptahydrate)	Sigma	M1880-500G
Milli-Q water
NaCl (Sodium Chloride)	Sigma	S9888-500G
NaHCO3 (Sodium Bicarbonate)	Sigma	S5761-500G
Omnifi t Q-series two hole bottle cap	Cole-Parmer	00945Q-2	To build 1 6-well array, need 1
PMP IPC-N L 24CHNL 8RLR 115V	MasterFlex	ISM939C-115V	24-channel peristaltic pump, require 1 for source and 1 for waste
Precision Seal® rubber septa,white, 7 mm O.D. glass tubing (100/pk)	Millipore Sigma	Z553905-100EA	To build 1 6-well array, need 6 septa
Propionic acid	Sigma	P5561
Pump Tubing, 2-Stop, Tygon S3 E-Lab, 1.02 mm ID; 12/PK	VWR	MFLX96460-28	To build 1 6-well array, need 6  (1 pack)
Pump Tubing, 2-Stop, Tygon S3 E-Lab, 1.14 mm ID; 12/PK	VWR	MFLX96460-30	To build 1 6-well array, need 6 (1 pack)
Puritan Cary-Blair Medium, 5 ml	Fisher Scientific	22-029-646
PYREX 2L Round Media Storage Bottles, with GL45 Screw Cap	Fisher Scientific	06-414-1E
Razor Blades	Genesee	12-640
Resazurin, sodium salt	ACROS Organics from ThermoFisher	AC41890-0010
Soluble starch	Sigma	S9765-100G
Stainless Steel Micro Spatulas, spoon like blade	Fisher Scientific	S50823
TBNG TYGON ELFL 2.06MMID 100'	VWR	MFLX06449-42	To build 1 6-well array, need 205.5 cm
Trace Mineral Supplement	ATCC	MD-TMS
Trypticase Peptone (BBL)	Fisher Scientific	B11921
Tubing, PTFE, 1/8″ (3.2 mm) OD × 1.5 mm ID, 10 M	Cole-Parmer	008 T32-150-10	To build 1 6-well array, need 300 mm
Tween 80	Sigma	P1754
Vitamin Supplement	ATCC	MD-VS
Yeast Extract (Bacto)	Fisher Scientific	DF0127-17-9