Skip to content

Brewing yeast and bacteria under the microscope

Cells from my own cultures and bottles, side by side: one row per organism, grouped by genus and cell shape. Click a thumbnail for the full photo; the sources column links every page that shows it.

In short

  • Cells from my own cultures and bottles under the microscope, side by side: Brettanomyces, Saccharomyces and Lactobacillus, grouped by genus and cell shape, one row per organism.
  • Why: shape and size are the first clues to what is in a bottle, and seeing them together shows what a description cannot.
  • Names are presumptive; a bottle isolate sits under the commercial strain it resembles, a likeness, not an identification.
  • Sizes are length x width in µm (Ø for round cells) from a calibrated camera, home-grade; photos without a scale say not to scale.
  • Nothing is blurred or retouched: busy fields are cropped, with an arrow.
  • Start with How to read this, or At a glance.

How to read this

  • Names are presumptive. Genus comes from cell shape, colonies and behaviour, never from an identification. A bottle isolate sits under the commercial strain it resembles; that is a likeness, not a match.
  • Size first, shape second. Where cells are measured, the group follows the measured length and width; phone shots are grouped by shape alone and marked not to scale.
  • Sizes are length x width in µm, or Ø for round cells, as a range with n, the number of cells measured. They come from a camera calibrated on a stage micrometer and the dregs analysis skill: edges to about ±0.1 µm, lines placed by hand to about ±0.3 µm. These are home-grade measurements.
  • Crops and arrows. Some photos are cropped from a busier field; an arrow marks the organism when others remain in the crop. The caption names the source page, which keeps the full field. Nothing is blurred or retouched.
  • Conditions are medium, days, temperature, stain and contrast, as I recorded them; "not recorded" where I did not.

At a glance

Genus Group Organisms Images Measured images
Brettanomyces Round to ovoid 2 7 6
Brettanomyces Elongated or cylindrical 5 19 7
Brettanomyces Ogival or apiculate 2 5 0
Saccharomyces Round to ovoid 2 2 1
Lactobacillus Short rods 1 1 0
Lactobacillus Long rods 1 2 1
Pediococcus no photos yet 0 0 0

Brettanomyces

Round to ovoid

Oval or egg-shaped cells with rounded ends, single, budding or in short chains. Brett A from Fair Isle Tove measures 3.9 to 6.6 x 2.3 to 4.3 µm, inside the Saccharomyces size range; it is narrower than the round Saccharomyces here (about 7 µm across), and often shows a bud at one narrow end [Med].

Organism Micrographs Size µm (n) Conditions Sources
Brettanomyces bruxellensis WLP648 Trois Vrai
WB-BUG-2026-002
strain: WLP648
anchor		 Clusters of ovoid, budding yeast cells of varying size, several budding pairs visible, 1000x oil immersion, no stain
live culture, 2026-05-01		 not to scale growth conditions not recorded
1000x, unstained		 WLP648 Trois Vrai - Brett
Fair Isle Tove, Brett A
WB-BUG-2026-022 Brett A
resembles WLP648
Shows oval and long cells, believed the same yeast.		 Oval cells, single and in pairs, one with a narrow bud at one end, with dimension lines on one oval cell, 6.5 by 3.5 µm, and one elongated cell, 4.8 by 1.9 µm
replate, 2026-10-23, measured Oval cells, some phase-bright, a 4.6 by 2.3 µm dimension on one cell, 1000x phase contrast
BRA-PL8, 2026-10-30, measured A chain of large oval cells with dimensions of 6.6 by 4.3 µm and 3.9 by 3.2 µm, 1000x phase contrast
colony 3, 2026-10-31, measured Two long cells joined end to end, a 5.3 by 2.0 µm dimension on one, 1000x phase contrast
colony 3, long cells, measured A chain of four long cells joined end to end among oval cells, a 10.1 by 3.2 µm dimension on the end cell and 4.0 by 2.4 µm on an oval cell, 1000x phase contrast
BRA-SA9, 2026-11-07, pseudohypha, measured Oval cells of mixed size and a large cell budding an elongated cell, a 4.4 by 3.0 µm dimension on an oval cell and 7.1 by 3.1 µm on the elongated bud, 1000x phase contrast
BRA-SA9, 2026-11-07, measured		 oval: 3.9 to 6.6 x 2.3 to 4.3 (7)
elongated: 4.8 to 7.1 x 1.9 to 3.1 (3)
pseudohyphal: 10.1 x 3.2 (1)		 growth conditions not recorded
wort agar, 7 days, 29 to 31 °C
wort agar, 8 days, 29 to 31 °C, then 4 °C for 1 day
saline (pooled colonies from wort agar)
1000x, phase contrast, unstained		 Fair Isle Tove

Elongated or cylindrical

Drawn-out cells, more than twice as long as wide, single or end to end in short chains. Brett B measures 3.2 to 4.9 x 1.3 to 2.0 µm. At a glance these pass for rods, but the rods from the same bottle are 0.5 to 0.6 µm wide, about three times thinner.

Organism Micrographs Size µm (n) Conditions Sources
Brettanomyces claussenii WLP645
WB-BUG-2026-001
strain: WLP645
anchor		 Elongate, tapered boat-shaped cells with visible internal granulation and a small budding pair at lower left, 1000x oil immersion, no stain
live culture, 2026-05-01 Single elongate, curved cell with a row of internal granules, 1000x oil immersion, no stain
live culture, 2026-05-01		 not to scale growth conditions not recorded
1000x, unstained		 WLP645 Claussenii - Brett
Fair Isle Tove, Brett B
WB-BUG-2026-022 Brett B
resembles WLP645
Teardrop cells among the long ones.		 The same chain with dimension lines on one long cell, 4.9 by 1.6 µm
same field, measured A short chain of long, pointed cells with a forked tip
round 2, 2026-10-23 Several chains of long, narrow cylindrical cells joined end to end, all alike, with dimension lines on one cell, 4.3 by 1.6 µm
BRB-TU12, 2026-10-25, measured The same cluster with dimension lines on one long cell, 4.8 by 1.9 µm, and one teardrop cell, 4.9 by 3.7 µm
same field, measured A branched cluster of long cylindrical cells joined to oval and teardrop-shaped cells
saline from round 2, 2026-10-25 Elongated cells, single and in short chains with small buds, a 4.4 by 1.4 µm dimension on one cell, 1000x phase contrast
BRB-PL10, 2026-10-30, measured A bent chain of long cylindrical cells and a pair beside it, a 4.3 by 1.5 µm dimension on one cell, 1000x phase contrast
BRB-TU12, 2026-10-25, measured Narrow ogival and cylindrical cells in pairs and short chains, a 3.8 by 1.6 µm dimension on one cell and 4.4 by 1.7 µm on another, 1000x phase contrast
BRB-SA15 top line, 2026-11-07, measured Narrow pointed oval and cylindrical cells, single and in a budding chain, a 5.5 by 1.5 µm dimension on one cell, 1000x phase contrast
BRB-SA17 stir line, 2026-11-07, measured		 elongated: 3.2 to 5.5 x 1.3 to 2.0 (17)
teardrop or lemon: 3.8 to 4.9 x 1.6 to 3.7 (2)		 growth conditions not recorded
wort agar, 7 days, 29 to 31 °C
wort, 2 days, ~30 °C
saline (pooled colonies from wort agar)
1000x, phase contrast, unstained		 Fair Isle Tove
Brettanomyces from Holy Goat Shrinebuilder
WB-BUG-2026-011
resembles WLP645
Near the ovoid boundary (length about twice the width); shiny and dull colony types combined.		 Small elongated and ogival yeast cells, many budding in pairs or short chains, 1000x oil immersion, phase contrast
2026-03-13 Cluster of oval and ogival yeast cells with budding pairs, cells of varying size, 1000x oil immersion, phase contrast
shiny and dull colonies, 2026-03-28		 not to scale growth conditions not recorded
1000x, phase contrast, unstained		 Isolating Organisms
Holy Goat Shrinebuilder
Holy Goat Shrinebuilder - Brett
Brettanomyces from Wild Beer Co Rooting Around
WB-BUG-2026-008
resembles WLP645		 Slender, elongated yeast cells, single and in short end-to-end chains, with some small round refractile cells and debris, 1000x oil immersion, phase contrast
2026-09-20 Scattered slender, elongated cells, some in pairs or short chains, a few with visible inclusions, 1000x oil immersion, phase contrast
2026-09-20 A long, thin filament of cells with a short side branch at one end, with shorter elongated cells scattered around, 1000x oil immersion, phase contrast
long chain, 2026-09-20 A long chain of elongated cells with bright inclusions, ending in a cluster of budding oval cells, 1000x oil immersion, phase contrast
chain ending in budding cells, 2026-09-20		 not to scale growth conditions not recorded
1000x, phase contrast		 WBC Rooting Around - Brett
Cantillon Long Brett
WB-BUG-2026-006 Long
resembles WLP645
First kept apart from Cantillon Tiny Brett; now banked mixed as one organism.		 Long, cylindrical yeast cells, some in short chains of two or three, with a few shorter oval cells, 1000x oil immersion, phase contrast
Long Brett, 2025 The same field, arrows on two long cylindrical cells on the left, 1000x oil immersion, phase contrast
banked mix; arrows on long cells; cropped from Cantillon Rosé de Gambrinus		 not to scale growth conditions not recorded
1000x, phase contrast		 Cantillon Rosé de Gambrinus
Cantillon Rosé de Gambrinus - Brett

Ogival or apiculate

Cells with one pointed end (ogival, teardrop) or both (apiculate, lemon-shaped). Lemon-shaped cells are also the mark of the wild yeast Hanseniaspora, so a lemon on its own does not mean Brett [Med].

Organism Micrographs Size µm (n) Conditions Sources
Brettanomyces bruxellensis Wyeast 5112
WB-BUG-2026-003
strain: Wyeast 5112
anchor		 Ovoid to oval yeast cells of varying size, several budding pairs and small groups, clear background, 1000x phase contrast
clear wort, 2026-09-20 Ovoid and elongate yeast cells, some joined end to end in short branching chains, and small clumps, 1000x phase contrast
clear wort, 2026-09-20 A short branching chain of elongate yeast cells and scattered single cells among small dark particles, 1000x phase contrast
DME starter, 2026-09-20		 not to scale growth conditions not recorded
1000x, phase contrast		 Wy5112 Bruxellensis - Brett
Cantillon Tiny Brett
WB-BUG-2026-006 Tiny
resembles Wyeast 5112
'Tiny' names the colony size, not the cells. First kept apart from Cantillon Long Brett; now banked mixed as one organism.		 Oval and elongated yeast cells, arrows on a lemon-shaped cell and a small oval cell, 1000x oil immersion, phase contrast
banked mix; arrows on oval and lemon-shaped cells; cropped from Cantillon Rosé de Gambrinus Three small oval to ogival yeast cells, well apart, one with a small bud, on a background with fine debris, 1000x oil immersion, phase contrast
Tiny Brett, 2025		 not to scale growth conditions not recorded
1000x, phase contrast		 Cantillon Rosé de Gambrinus
Cantillon Rosé de Gambrinus - Brett

No photo yet: Brettanomyces Bootleg Biology Funk Weapon #1 (anchor).

Saccharomyces

Round to ovoid

Round to oval cells budding singly or in small clusters, larger and rounder than most Brett. The Wy3278 isolate measures about 7 µm across (6.1 to 8.2 µm, n = 5, on an extrapolated scale).

Organism Micrographs Size µm (n) Conditions Sources
Saccharomyces from Wyeast 3278 Lambic Blend
WB-BUG-2026-010
Scale extrapolated to 400x.		 Round yeast cells in clusters and singly, with a 7.0 µm diameter line on one cell, phase contrast
slurry, measured (extrapolated scale)		 oval: Ø 6.1 to 8.2 (5) slurry
400x, phase contrast, unstained		 Wy3278 Lambic Blend - Sacch
Holy Goat Shrinebuilder, Saccharomyces isolate (discarded)
WB-BUG-2026-016 Saccharomyces		 Round to oval yeast cells, singly and in small clusters, some with visible granules, 1000x oil immersion, phase contrast
2026-03-13		 not to scale growth conditions not recorded
1000x, phase contrast, unstained		 Holy Goat Shrinebuilder

No photo yet: Saccharomyces cerevisiae Wyeast 3726 Farmhouse Ale (anchor).

Lactobacillus

Short rods

Rods up to about four times as long as wide, single, in pairs or short chains, far thinner than any yeast here.

Organism Micrographs Size µm (n) Conditions Sources
Lactobacillus Painintheassus (Wild Beer Co Rooting Around)
WB-BUG-2026-015		 Many short rod-shaped cells, single, in pairs and in short chains, with a few small round particles and faint purple-tinged debris, 1000x oil immersion, phase contrast
2023-04-04		 not to scale growth conditions not recorded
1000x, phase contrast		 WBC Rooting Around
WBC Rooting Around - Lacto

Long rods

Thin rods more than four times as long as wide, single or as long curved filaments. The Tove rods measure 4.1 x 0.5 µm and 11.5 x 0.6 µm.

Organism Micrographs Size µm (n) Conditions Sources
Fair Isle Tove, Lacto (never isolated)
WB-BUG-2026-022 Lacto		 Thin dark rods, singles and a long curved filament, with measurements of 4.1 by 0.5 µm and 11.5 by 0.6 µm marked
top-layer tube, 2026-10-01, measured Thin dark rods, a pair and a long curved filament, marked with arrows, out-of-focus cells behind, 1000x phase contrast
same top-layer frame, wider crop; arrows on rods		 rods: 4.1 x 0.5 (1)
filament: 11.5 x 0.6 (1)		 growth conditions not recorded
1000x, phase contrast, unstained		 Fair Isle Tove

Pediococcus

No photos yet. Expect tiny round cells in pairs and groups of four (tetrads) [1].

Gaps

Banked organisms with no usable micrograph yet:

No photos yet for: Pediococcus, other organisms (acetic acid bacteria, wild yeasts, moulds).

References

  1. Oregon Brew Lab. 5 Beer Spoilage Signs Every Brewer Should Know: Pediococcus Edition. https://oregonbrewlab.com/5-beer-spoilage-signs-every-brewer-should-know-pediococcus-edition/

Built from the register on 2026-11-08: 36 images, 13 organisms.