This article is part 3 of a 3-part series.
You can view part 1 of this series here.
You can view part 2 of this series here.

Spores vs Non-Spores Organisms

We believe this is probably one of the most important topics to understand when discussing biological inoculants because it helps shed light on why some organisms need to be handled more cautiously than others. This is not from a danger standpoint, but rather from a viability standpoint.

What is a Spore?

A very basic definition of a spore is that it is a dormant survival cell. By nature, spores are durable and can survive in less than ideal conditions. All fungi produce spores; however, not all bacteria produce spores! Furthermore, fungal spores and bacterial spores are different in how they function and how they are produced.

What are Fungal Spores?

Fungal spores are used to help fungi reproduce asexually (some fungi can also reproduce sexually). As an organism becomes mature or stressed, the fungal cells begin to produce spores as a means to propagate. Fungal spores are single cells that will float through the air, looking for a favorable environment to begin developing. Fungal spores are very hearty and can survive for years in unfavorable conditions. However, compared to bacterial spores they are less durable.

Fun fact: Trichoderma spores can number up to 10-20 billion in a single gram of pure spores!

What are Bacterial Spores?

Bacterial spores are meant for survival in stressful conditions and are not for reproduction, like fungi spores are. The actual living cell, called the vegetative cell, produces a protective layer (spore) around its DNA until favorable conditions return. Bacterial spores are extremely durable and can be very difficult to destroy even under extreme temperatures. Bacterial spores can survive drought, extreme temperatures, and low pH.  Once favorable conditions return, the protective proteins dissolve the spore coating and the vegetative cell functions resume.

Fun fact: Scientist have discovered viable bacterial spores that are millions of years old.

Non-Spore Forming Bacteria

Compared to their spore-forming counterparts, non-spore forming bacteria are more susceptible to environmental stresses like heat and desiccation.  Inoculant products containing these types of organisms need to be cared for properly in order to protect the health and viability of the. Hence, why you may want to rethink leaving your legume inoculant in your sunbaked truck!

Spore Producer                                Non-Spore Producer

Trichoderma (Fungus)                                                 Bradyrhizobia (Bacteria)

Clonostachys     (Fungus)                                            Rhizobia (Bacteria)

Mycorrhiza (Fungus)                                                   Pseudomonas (Bacteria)

Bacillus (Bacteria)        

First Photo: Bacteria Spores

Second Photo: Fungal Spores