What is the shape of Bartonella?

The shape and shape variation of Bartonella

Bartonella can take almost any shape. Within a cell, the most common is the coccus, or close to a sphere, but there are also species that are slightly elongated outside the cell, stick shape show.

A coccobacillus term that refers to their form is a perfect description of this: the coccus form represents the spherical shape, while the bacillus form the shorter, stickier look.

Members of the genus Bartonella are small, pleomorph, i.e. coccobacilli of variable shape. They take many shapes, from round to slightly elongated, depending on the test method and medium used. Of the dozens of known species confirmed in 12 species, that it can cause human infection, but three species are most commonly used in human diagnostics.

1. Figure 1: Image of Bartonella according to Wikipedia

A photograph can have a significant impact on the mental image we have of a bacterium. It's easy to think of bacteria as „posed”, waiting to be photographed, but they are actually part of constantly changing, dynamic systems.

It is impossible to capture bacteria in their natural environment, as hundreds of times magnification is required. This requires taking the sample out of the host, which in itself can change the shape, movement and reproduction of the bacteria.

Magnification is most commonly performed with a microscope, but imaging techniques other than the traditional light microscope are now available. The different methods all end up producing an image that can be interpreted by the human eye, but these images do not always accurately reflect the natural state of the bacterium.

2. Figure 1: Bartonella in an educational material, inside a red blood cell (Giemsa staining)

Figure 3: Dark field image of Borrelia in stationary liquid culture and immunofluorescence image of Borrelia moving in simulated blood stream.

Effect of sample preparation on the shape of the bacterium

Once the sample has been taken, it is usually not possible to place the sample under the microscope immediately. Bacteria are often present in low numbers - even in the case of Bartonella infections, which cause severe symptoms - so in many cases they must be propagated or concentrated. During the culture process, the shape of the bacteria can change.

A good example of this is Borrelia, which can even modify the proteins responsible for movement in just a few generations. For this reason, the naturally undulating spirochete often appears in a very different form in laboratory images. Bartonella can change shape in a similar way.

Staining procedures and additional distortions

If the sample is not examined under a darkfield microscope, it is necessary to non-specific (e.g. Giemsa) or specific (immunofluorescent) for painting. Without this, Bartonella would be barely visible, as the pathogens are not coloured in their natural state and are barely distinguishable from their environment.

Figure 4: Dark field image of Bartonella in the red blood cell

Figure 5: Electron micrograph of Bartonella bacilliformis (a bacillus, i.e. a species with a pickle-like shape) in the process of infiltration into the red blood cell

Painting processes can cause further deformation. The dyes bind to the bacterial genome or proteins, while the solvent can change the pH of the sample. Some methods reveal only the interior of the cell, others only the surface proteins, so that even the apparent size of the bacterium may change.

Electron microscopy often requires freezing, which can also distort or even destroy the original structure of the bacteria.

The role of intracellular and extracellular location

Bartonella is often in red blood cells or epithelial cells where it can evade the immune system's attack. However, it can also occur in the blood plasma, outside the cell.

The location has a significant influence on the shape. Inside the cell, it can take a more rounded shape, while outside the cell, a more elongated, stick-like appearance is more common.

Figure 6: different species of Bartonella in red blood cells, lymph node, immunofluorescence

Summary

The shape of Bartonella can be extremely varied, ranging from a spherical shape to a short stick-like shape. The shape of the bacterium is significantly affected

• the test method
• the breeding environment
• the painting process
• and whether it is inside or outside the cell

Therefore, a single microscopic image alone does not give a complete picture of the true appearance of Bartonella. In its natural state, the bacterium can be pleomorphic, i.e. it can exist in several forms.