---
icon: 🦠
order: 2
---

# Microbes That Don’t Run on Glucose

Many familiar bacteria get energy by breaking down sugars like **glucose**. The groups below use **other** sources of energy—light, inorganic chemicals, or unusual compounds—so their “fuel” is not carbohydrate metabolism in the usual sense.

## Chemolithotrophs (energy from inorganic chemicals)

| What they oxidize (energy source) | Examples (genera / groups) |
|-----------------------------------|----------------------------|
| **Hydrogen** (H₂) | *Hydrogenovibrio*, *Cupriavidus* (some strains), many deep-sea and vent-associated bacteria |
| **Ammonia** → nitrite | *Nitrosomonas*, *Nitrosococcus* (ammonia-oxidizing bacteria) |
| **Nitrite** → nitrate | *Nitrobacter*, *Nitrospira* (nitrite-oxidizing bacteria) |
| **Hydrogen sulfide** / sulfur | *Thiobacillus* (*Acidithiobacillus*), *Beggiatoa*, sulfur-oxidizing ε-proteobacteria near vents |
| **Iron** (Fe²⁺ → Fe³⁺) | *Gallionella*, *Leptothrix*, *Acidithiobacillus ferrooxidans* (acid mine drainage and iron mats) |
| **Manganese** | *Leptothrix*, *Crenothrix* (some manganese-oxidizing bacteria) |
| **Arsenic** (As³⁺ ↔ As⁺⁵) | *Halomonas* strain in Mono Lake–type systems; arsenic redox bacteria in contaminated aquifers |
| **Methane** (as sole energy source, not sugar) | Methanotrophs: *Methylomonas*, *Methylococcus*, *Methylosinus* (oxidize CH₄) |

## Phototrophs (energy from light, not from glucose)

These fix carbon with CO₂ (or simple organics) but **capture energy with pigments**, not by eating glucose.

| Type | Examples | Notes |
|------|----------|--------|
| **Oxygenic photosynthesis** | *Synechococcus*, *Prochlorococcus*, many **cyanobacteria** | Like plants: light + H₂O → O₂ |
| **Anoxygenic photosynthesis (sulfur)** | *Chromatium*, *Thiocapsa* (purple sulfur bacteria) | Light + H₂S or S instead of glucose |
| **Anoxygenic (non-sulfur purple bacteria)** | *Rhodobacter*, *Rhodospirillum* | Often use light + organic acids or H₂; not primarily glucose-dependent in the same way as lab *E. coli* |

## Archaea (often grouped with “weird energy” bacteria in conversation)

Strictly, these are **Archaea**, not Bacteria, but they illustrate “non-glucose” energy:

- **Methanogens** (*Methanobacterium*, *Methanosarcina*): energy from H₂ + CO₂, or acetate, or methyl compounds—not from sugar oxidation like respiration of glucose.
- **Hyperthermophiles** at vents: many use H₂, sulfur, or iron (*Sulfolobus*, *Pyrococcus*).

## Short takeaway

**Glucose** is one option among many. **Chemolithotrophs** eat rocks and dissolved ions; **phototrophs** eat photons; **methanotrophs** eat methane; **methanogens** (archaea) build methane or run on hydrogen. Together they show life’s habit of wiring almost any redox gradient into ATP.