1986 Bergey's Manual Bacillus

The 1986 Bergey's Manual of Systematic Bacteriology provides comprehensive classification and identification information for Bacillus species. Bacillus is a genus of Gram-positive, rod-shaped bacteria known for forming endospores, aerobic or facultative anaerobic metabolism, and widespread distribution in various environments. Below are key sections covering classification, characteristics, identification methods, and applications.

Classification Overview

Bacillus species are classified within the family Bacillaceae, order Bacillales, class Bacilli, phylum Firmicutes. The genus includes both pathogenic and non-pathogenic species with diverse ecological roles.

Morphological Characteristics

Bacillus species exhibit distinct morphological features that aid in identification and classification.

1. Cell morphology: Straight rods, 0.5-2.5 μm wide, 1.2-10 μm long.
2. Endospores: Oval or cylindrical, central or terminal position, resistant to heat and chemicals.
3. Colony appearance: Creamy, white, or pigmented colonies on agar media.
4. Motility: Most species are motile with peritrichous flagella.

NOTE! Spore position and colony morphology are key diagnostic features for species differentiation.

Biochemical Properties

Biochemical tests are essential for accurate identification of Bacillus species.

1. Catalase test: Typically positive for most Bacillus species.
2. Oxidase test: Variable among species.
3. Gelatin hydrolysis: Positive for many species.
4. Starch hydrolysis: Variable; used for species differentiation.
5. Nitrate reduction: Species-dependent characteristic.
6. Carbohydrate fermentation: Patterns vary by species.

IMPORTANT! Biochemical profiles must be interpreted in conjunction with other identification methods.

Growth Requirements

• Temperature: Mesophilic (20-45°C), some thermophilic species exist.
• pH Range: 5.5-8.5 optimal for most species.
• Nutrition: Chemoorganotrophic, utilizing various carbon sources.
• Salt Tolerance: Varies by species; some tolerate up to 7% NaCl.
• Oxygen: Aerobic to facultative anaerobic.
• Media: Nutrient agar, blood agar, specialized selective media.

Identification Methods

Comprehensive identification involves multiple approaches for accurate species determination.

Conventional Methods: Gram staining, spore staining, biochemical tests, growth characteristics.

Morphological: Cell shape, spore morphology, colony characteristics. Biochemical: Catalase, oxidase, gelatin hydrolysis, carbohydrate utilization. Physiological: Temperature and pH optima, salt tolerance. Molecular: DNA hybridization, 16S rRNA sequencing (emerging method in 1986).

Common Species

Key Bacillus species with distinctive characteristics and habitats.

1. Bacillus subtilis: Model organism, soil bacterium, industrial applications.
2. Bacillus cereus: Food spoilage, opportunistic pathogen.
3. Bacillus anthracis: Causative agent of anthrax.
4. Bacillus thuringiensis: Insect pathogen, biopesticide.
5. Bacillus licheniformis: Soil bacterium, enzyme production.

Tip: Proper species identification requires comprehensive testing and reference to type strains.

Pathogenic Species

Several Bacillus species are medically important pathogens requiring special handling.

1. Bacillus anthracis: Causes anthrax in humans and animals.
2. Bacillus cereus: Food poisoning, eye infections, opportunistic infections.
3. Virulence factors: Toxins, capsules, hydrolytic enzymes.
4. Transmission: Inhalation, ingestion, cutaneous contact.
5. Laboratory safety: BSL-2 or higher for pathogenic species.

WARNING! Handle pathogenic Bacillus species in appropriate biosafety conditions. Follow established safety protocols.

Industrial Applications

Bacillus species have numerous industrial and commercial applications.

Enzyme Production: Amylases, proteases, cellulases. Antibiotic Production: Bacitracin, polymyxin. Biocontrol: B. thuringiensis as biopesticide. Food Industry: Fermentation processes. Biotechnology: Protein expression systems.

Laboratory Procedures

Standard laboratory methods for isolation and identification of Bacillus species.

Isolation: Heat treatment (80°C, 10 min) for spore selection. Staining: Gram stain, spore stain (malachite green). Culture: Nutrient agar, selective media. Preservation: Lyophilization, glycerol stocks at -80°C.

CAUTION! Follow aseptic techniques and proper disposal procedures for all bacterial cultures.

References

Sneath, P.H.A., Mair, N.S., Sharpe, M.E., & Holt, J.G. (Eds.). (1986). Bergey's Manual of Systematic Bacteriology, Volume 2. Williams & Wilkins. Additional references: Gordon et al. (1973), The Genus Bacillus; Claus & Berkeley (1986), Genus Bacillus Cohn 1872.

Troubleshooting Identification

Quality Control: Use reference strains for method validation.

Expert Consultation: Contact specialized microbiology laboratories for difficult identifications.