Plant surfaces or the interior walls of animal intestines grow slowly or are difficult to culture; these bacteria are referred to as being viable but non-culturable. Despite many efforts to improve culture conditions by altering nutrient components, pH or other physicochemical conditions, few breakthroughs have been achieved in culturing VBNC bacteria to date. Some studies have found that replacing agar with gellan gum in solid media accelerates the growth of slow-growing bacteria, particularly those from soil or rhizosphere that utilize only extracellular polysaccharides, xanthan and gellan as their carbon source. We have also found that some slow-growing soil bacteria in the soil bed from a boreal larch forest generated minute colonies on 1.0% agar plates containing modified U0126 Winogradsky’s medium, although they proliferated well and formed swarmed colonies on 1.0% gellan plates in MW. Pseudomonas collierea V5-G’5 isolated from isolated from an East Siberian larch forest bed soil exhibited clearly distinguishable behaviours on the plates of agar and gellan. Conversely, MW plates containing 1.0 or 1.5% gellan gum that had been previously washed with MeOH slightly repressed the swarming of P. collierea V5- G’5. In contrast, the swarming or swimming of P. collierea V5- G’5 was completely abolished on 0.5 to 0.7% unwashed agar in the same medium despite high wettability, whereas medium containing 0.5% or even 0.75% agar that had previously been washed with MeOH allowed the bacterial cells to swarm. Although MW plates containing 0.25 to 2.0% MeOH-washed gellan gum slightly repressed V5-G’5 swarming, P. collierea V5- G’5 still formed swarmed colonies that were clearly larger than those on MW plates with the same concentrations of washed agar. In addition, 10-fold higher concentrations of gellan gum extracts did not induce V5-G’5 swarming on plates containing 0.5 to1.5% unwashed agar. We therefore hypothesised that MeOH-soluble chemical constituents in agar are the primary factors that inhibit swarming of P. collierea V5-G’5 on agar plates, as reported previously in some studies on swarming inhibitors. Most bacteriologists over approximately the past century have used agar containing the furan-2-carboxylic acids as the gelling material for plate cultures. On these plates, many bacteria grow as individual colonies of a manageable size that do not overwhelm neighbouring colonies due to swarming or swimming suppression by the furan-2-carboxylic acids in processed agar. However, these properties also result in agar being an inappropriate solid medium for studying most slow-growing, oligotrophic environmental bacteria. The presence of 5- HMFA, FA and potentially other unknown compounds in agar may lead to in many bacteria assuming the VBNC or slowgrowing state, whereas gellan gum, which has no 5-HMFA, often allows the proliferation of some VBNC bacteria regardless of nutritional demands. We also consider the presence of some quormone mimic or surfactant as a fluidising component in the gellan gum, probably allowing the bacterial swarming on gellan plates to be visible as a single colony. The identification of these important functions of 5-HMFA and FA could be a significant breakthrough to improve bacterial culture. Inhibiting this bacterial behaviour on solid medium by adding extremely low concentrations of 5-HMFA and FA would be of great benefit for the study of many species of bacteria that are grown on solid agar media. Recent advances in understanding the mechanisms of how swarming and swimming are regulated have shown that many bacteria share systems for regulating these behaviours.