Bacillus pumilus

Introduction

Bacillus pumilus is a spore-forming, aerobic bacterium valued in composting for its ability to degrade organic matter under stressful conditions. Known for surviving heat, salt, and oxidative environments, it contributes to the breakdown of proteins, starches, and plant residues even when compost conditions are suboptimal. It’s often included in fortified compost inoculants to improve resilience and microbial diversity.

Scientific Description

B. pumilus belongs to the family Bacillaceae. It produces a variety of extracellular enzymes (amylase, protease, pectinase) and has notable resistance to UV, heat, and salinity. In compost, it participates during the thermophilic and curing phases, supporting microbial succession and helping sanitize the pile.

Benefits

• Resilient Decomposer: Works in heat, oxidative stress, and varying moisture.
• Breaks Down Proteins and Starches: Complements Bacillus subtilis and licheniformis.
• Controls Odors and Pathogens: Outcompetes foul-smelling anaerobes.
• Improves Compost Shelf Life: Contributes stable spores that remain active in stored compost.
• Stimulates Root Colonization Post-Application: Functions as a mild PGPR when compost is applied to soil.

Uses

• Waste Types: Food waste, vegetable market leftovers, meat scraps, protein-rich residues, paper sludge.
• Methods: 1–2 kg/ton in composting mixes, often used with Bacillus subtilis and Trichoderma.
• Timing: During pile formation and first 7–10 days of thermophilic phase.

Trivia

• Its spores can resist autoclaving — studied for spacecraft sterilization protocols.
• Some strains used in plant disease suppression due to antifungal enzyme activity.