摘要:

Two soil organisms,Arthrobacter pascensandArthrobacter terregens, the first producing a growth-promoting substance, the "terregens factor", and the second requiring it, pass through a complex morphological life cycle. Two kinds of aged cells are found of which, on transfer to fresh medium, one forms a cystite which 'germinates' and looses free cells from a ruptured tube, the other follows the usual course of 'normal' cell division. The similarity in form to that of the type speciesArthrobacter globiformeis quite distinct.

ISSN:0008-4166    

DOI:10.1139/m57-013

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Six organisms belonging to the genusArthrobacterand showing a requirement for the terregens factor (TF) have been studied and compared with the original test organism,Arthrobacter terregens. All seven organisms are alike in that they are stimulated not only by the terregens factor but also by certain related substances that contain iron, namely coprogen, ferrichrome, and hemin. TF response is also obtained with aspergillic acid, soil extract, and liver extract. On the basis of their physiological characteristics and nutritional requirements, the organisms were grouped into four types. Growth curves ofA.terregensand one other organism, based on response to TF, suggest their suitability for use in the microbiological assay of the factor.

ISSN:0008-4166    

DOI:10.1139/m57-014

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Nodulation responses and certain other characteristics of a mutant soybean line highly recalcitrant to nodulation were compared with those of a nodulating sister line. Roots of the two lines were found to harbor equal numbers of rhizobia. Stem graftings to provide top growths of one line on roots of the other failed to alter the distinctive nodulation responses of rootstocks. Ascorbic acid contents in the two lines were identical, both in the tops and in the roots, although contents in tops greatly exceeded those found in roots. Chromatographic studies on the amino acids in seed hydrolyzates and in alcoholic extracts of seedlings showed no differences between the two lines either in kind or quantities of amino acids. In a survey of stock rhizobia for cultures effective on the nonnodulating line, bacteria were discovered which formed nodules on such soybeans growing in sand and nutrient solution. Isolates from these nodules again yielded effective nodulation on plants in sand culture, but gave no nodulation whatsoever on plants growing in soil. This negative response was confirmed in three different soils. Admixtures of soil and of miscellaneous materials with sand were employed to alter nodulation responses from those shown in sand cultures.

ISSN:0008-4166    

DOI:10.1139/m57-015

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Detection of bacteria other thanRhizobiumin nodule cultures led to studies on bacteria existing within normal clover roots. Those isolated from clover root tissue appeared to fall into five groups on the basis of morphology and biochemical characteristics. The identity of three of the groups was tentatively established respectively asAerobaclcr cloacaeJordan, Bergeyet al.,Bacillus megatheriumDe Bary, andFlavobacterium rhenanus(Migula) Bergeyet al.

ISSN:0008-4166    

DOI:10.1139/m57-016

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

In field experiments with oats the composition of the bacterial population in the rhizosphere was found to be almost stable during the whole period of plant development from young seedlings to maturity. In the beginning of the growth season the soil flora was quite different from that of the rhizosphere. It was, however, successively changed, and became, toward the end of the season, similar in composition to the rhizosphere population. This change proceeded from the soil surface into deeper soil layers, and it can be concluded that it was due to the development of roots, and to a migration of bacteria from the rhizosphere into the soil.

ISSN:0008-4166    

DOI:10.1139/m57-017

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

A test has been made of Bliss's hypothesis that when infected tree roots are fumigated with carbon disulphide,Armillaria melleais killed not by direct fungicidal action, but through the agency ofTrichoderma viride, which is relatively tolerant of the fumigant and becomes dominant in the treated soil. Bliss's observation thatT.viridebecomes much more abundant in soil after fumigation was confirmed, though higher dosages of carbon disulphide tended to select still more resistant fungi, such as ascosporic penicillia of theP.luteumseries. When small woody inocula ofA.melleahad been incubated for 3 weeks in soil that had been previously fumigated with carbon disulphide at the rate of 828 p.p.m. and then kept for 3 weeks before use, 30% of the inoculum segment-ends failed to produce rhizomorphs when placed in tubes of fresh soil for a viability test. Nevertheless, this indirect effect of soil fumigation cannot wholly account for the total loss of viability when inocula ofA.melleaare directly fumigated in soil. It seems, therefore, that carbon disulphide must directly damage at least the peripheral mycelium ofA.melleain the woody host tissues, and so facilitate invasion byT.virideand/or other fungi. With this additional postulate, Bliss's hypothesis seems to account well for all the observed facts.

ISSN:0008-4166    

DOI:10.1139/m57-018

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Three groups of bacteria capable of decomposing chloro-substituted aliphatic acids were isolated from soil by means of selective media. A group ofPseudomonas-like bacteria (A) decomposed monochloroacetate (and monobromoacetate) readily in media with yeast extract, peptone, or amino acids. They also decomposed α-monochloropropionate with moderate vigor, but had little effect on dichloro-acetate and -propionate, and none on trichloroacetate. A non-sporeforming bacterium of uncertain taxonomic position (B) was able to decompose trichloroacetate in media containing soil extract or vitamin B12, and also in basal medium when associated with vitamin B12-producing strains ofStreptomyces. Dichloroacetate was only slightly attacked, and monochloroacetate and α-dichloropropionate not at all. A group of bacteria (C) apparently belonging toAgrobacteriumdecomposed α-dichloropropionate and dichloroacetate, but was less active towards α-monochloropropionate, and did not attack mono- and tri-chloroacetate. The organisms of groupsBandCgrew only feebly in ordinary media. The decomposition of monochloroacetate, trichloroacetate, and α-dichloropropionate in soil was accelerated by addition of cell suspensions of groupsA,B, andC, respectively. The organisms seemed to be more active in the soil thanin vitro.

ISSN:0008-4166    

DOI:10.1139/m57-019

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Pseudomonas aeruginosawas grown under conditions suitable for pyocyanine production in a medium containing glycerol,L-leucine,DL-alanine, calcium carbonate, salts, and small amounts of various C14-labelled substrates. A comparison of the specific activities of the cell carbon, respiratory carbon dioxide, and pyocyanine carbon showed that glycerol and dihydroxyacetone were the only substrates from which pyocyanine having a specific activity higher than the cell carbon was formed. Glucose, fructose, pyruvate, acetate, and the 13 amino acids tested were inferior in this respect. Alanine, leucine, isoleucine, and glycine were incorporated into pyocyanine more readily than the other amino acids. Phenylalanine and tyrosine, although possessing preformed rings, were poor precursors of pyocyanine and were oxidized more readily than they were assimilated. These results suggest that pyocyanine originates from trioses but gives little indication of the nature of the intermediates.

ISSN:0008-4166    

DOI:10.1139/m57-020

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Bacteriophage for clover nodule bacteria can be found on roots and nodules of all naturally grown clover plants and also in the soil surrounding the roots, but not in soil without clover plants. Alternative hosts for the phage of clover bacteria are pea bacteria, and vice versa. The bacteria and the phage are heterogeneous in the sense that only a proportion of strains of clover bacteria and of pea bacteria are susceptible to lysis by a given race of phage, and only a proportion of races of phage can lyse a given bacterial strain. There does not seem to be any association between the susceptibility of bacterial strains to lysis by phage and any other features such as antigenic structure and effectiveness in nitrogen fixation. There may be an association with avirulence, i.e. inability to infect the host plant. The behavior of phage–bacterial mixtures depends on the surrounding medium. The longevity of phage in soil or in a soil-like medium such as a vermiculite mixture is relatively short, and the effect of phage can be localized so that phage-susceptible bacteria and the phage can exist close to each other without any apparent interaction. However, as long as the phage is present, phage-resistant bacterial mutants are usually present also. The phage-resistant mutants may also be mutants in other respects such as effectiveness in nitrogen fixation. In the presence of weakened phage, bacterial mutants were found to occur that differ from the parent form in effectiveness but resemble it in susceptibility to the phage.

ISSN:0008-4166    

DOI:10.1139/m57-021

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

A study was made of the host affinities of fourLotusrhizobiophages for 91 rhizobial strains from 10Lotusspp., 376 strains of other rhizobia, and 40 strains of species in the generaAgrobacteriumandChromobacterium. No one phage lysed every rhizobial strain of theLotusspp.; however, all of the phages lysed every strain fromLotus angustissimus. None of the strains fromLotus uliginosuswas susceptible. Among rhizobia from the other eightLotusspp. all strains were lysed by at least one of the four phages. Of the 376 strains of other rhizobia, 28 strains of six plant genera were lysed by one or more of the fourLotusphages. None of the phages lysed any of the strains of species in the generaAgrobacteriumandChromobacterium.

ISSN:0008-4166    

DOI:10.1139/m57-022

出版商:NRC Research Press    

年代:1957

数据来源: NRC