Some Factors Influencing the Growth and Survival of Rhizobia in Humus and Soil Cultures

Abstract

A study was made of the growth of rhizobia outside the host plant in three high humus mixtures and a mineral soil. Rhizobia grew better in pure cultures than in an unsterile base. Incubation in Erlenmeyer flasks gave, as a rule, higher counts than in paper cartons. Addition of a mixture of sucrose, calcium carbonate, sodium chloride, dipotassium phosphate, and magnesium sulphate led to increased numbers of rhizobia in pure culture in all bases used, and produced increased numbers in the unsterilized mineral soil also. Addition of this mixture to the unsterile high humus bases increased the total numbers of bacteria, but not the number of rhizobia. When the bases were sterilized, the highest counts of rhizobia were obtained in the high humus bases. When sterilization was not carried out, the greatest numbers of rhizobia occurred in the mineral soil. In tightly stoppered flasks that did not permit aeration, the rhizobia appeared to die out completely when stored for more than a few days, whereas in loosely stoppered flasks the counts remained at a high level until the base became desiccated.

Some Factors Influencing the Growth and Survival of Root Nodule Bacteria in Peat Culture

“…The deleterious effect of desiccation of the peat carrier on the survival of rhizobia has been noted by Hedlin & Newton (1948) and by Waters (cited by Vincent, 1955).…”

“…Rhizobia grew and survived better in containers allowing free exchange of gas (Hedlin & Newton, 1948;van Schreven, Otzen & Lindenbergh, 1954). Rhizobia grew and survived better in containers allowing free exchange of gas (Hedlin & Newton, 1948;van Schreven, Otzen & Lindenbergh, 1954).…”

“…Rhizobia grew and survived better in containers allowing free exchange of gas (Hedlin & Newton, 1948;van Schreven, Otzen & Lindenbergh, 1954). When aeration was restricted, pure cultures grew better than contaminated cultures (Hedlin & Newton, 1948). When aeration was restricted, pure cultures grew better than contaminated cultures (Hedlin & Newton, 1948).…”

“…THERE ARE SEVERAL conflicting reports on the effect of gaseous exchange on the growth and survival of rhizobia in peat culture. Rhizobia grew and survived better in containers allowing free exchange of gas (Hedlin & Newton, 1948;van Schreven, Otzen & Lindenbergh, 1954). However, other workers have reported satisfactory survival in either screwcapped jars or sealed cans (Newbould, 1951; Spencer & Newton, 1953;Gunning & Jordan, 1954).…”

“…However, other workers have reported satisfactory survival in either screwcapped jars or sealed cans (Newbould, 1951; Spencer & Newton, 1953;Gunning & Jordan, 1954). When aeration was restricted, pure cultures grew better than contaminated cultures (Hedlin & Newton, 1948). Newbould (1951) obtained counts of RhizobiTLm meliloti as high as 58xlQ6/g of nonstwile peat after 4 months storage in cans.…”