Pure culture and reconstitution of the Anthoceros-Nostoc symbiotic association

Abstract

The partners of the symbiotic association between Anthoceros punctatus L. and Nostoc spp. have been cultured separately in a pure state. The symbiotic association was reconstituted following dual culture in liquid Anthoceros growth medium with a variety of axenic Nostoc isolates and mutant strains. The heterocyst frequency of competent Nostoc strains increased four- to fivefold when in symbiotic association relative to free-living N2-grown cultures. Dinitrogen fixation by symbiotic Nostoc supported the growth of Anthoceros tissue, although this growth was nitrogen-limited relative to that supported by exogenous ammonium. When the association was reconstituted in the presence of two or three wild-type and mutant Nostoc strains some of these strains were found to compete in infection of Anthoceros tissue and a fraction of the symbiotic Nostoc colonies contained more than one strain. Exogenous ammonium did not affect infection, but repressed development of the symbiotic Nostoc colonies in Anthoceros tissue, and symbiotic Nostoc in N2-grown Anthoceros tissue appeared to regress from the symbiotic state in the presence of exogenous ammonium. The results show that the Anthoceros-Nostoc symbiotic association is amenable to specific experimental manipulations; their implications are discussed with respect to infection of Anthoceros tissue and control of the development of symbiotic Nostoc.

Reconstitution of the symbiosis of Gunnera manicata Linden: cyanobacterial specificity

“…Interestingly, the infective strains Nostoc 7901 and Nostoc 8001 were shown to have a DNA restriction fragment length polymorphism (RFLP) pattern different from that of the non-infective Nostoc 8002 and Nostoc 8005 when hybridized either to a glnA or to a nifH probe (Zimmerman & Bergman, 1990). (Schmidt, 1991), metabolic adjustment (heterotrophy, N export, slow growth) The data presented here to a large extent resemble those obtained on the reconstitution of the Anthoceros-Nostoc symbiosis (Enderlin & Meeks, 1983). Out of the strains used in both studies, those infecting G. manicata also infected the hornwort Anthoceros punctatus L. and those that were noninfective on Anthoceros were also non-infective on G. manicata.…”

Transposon mutagenesis of Nostoc sp. strain ATCC 29133, a filamentous cyanobacterium with multiple cellular differentiation alternatives

“…Strain UCD 328 was found to be more sensitive than wild-type Nostoc 291 33 to a hormogonia-inducing factor in A. pzlnctatzls growth-conditioned medium (M. F. Meeks, unpublished). Furthermore, unlike other Nostoc strains, which may grow to a high density in the medium surrounding the plant (Enderlin & Meeks, 1983), epiphytic growth of strain UCD 328 was severely reduced; strain UCD 328 showed no obvious growth defect in the free-living state.…”

“…strain UCD 7801 (Fig. l), our original isolate from A. punctatzis (Enderlin & Meeks, 1983). Strain UCD 328 was found to be more sensitive than wild-type Nostoc 291 33 to a hormogonia-inducing factor in A. pzlnctatzls growth-conditioned medium (M. F. Meeks, unpublished).…”

“…Escbericbia coli strains were routinely cultured in Luria-Bertani (LB) broth (Sambrook e t al., 1989) and cell concentrations determined by measuring the optical density of cultures at 600 nm (OD6oo). Sources and culture conditions for symbiont-free and Nostoc-associated Antboceros pzmtatus, and all free-living Nostoc strains, were described previously (Enderlin & Meeks, 1983). The basal medium for growth of Nostoc was that of Allen & Arnon (1955) (AA) supplemented with 5 mM MOPS, pH 7.8 (-N), and, when specified, 2.5 mM NH,C1 ( + N ) ; it was used at full strength when solidified with 1 % (w/v) agar (purified using the methods of Braun & Wood, 1962) or diluted fourfold in liquid culture (AA/4).…”

“…Moreover, Nostoc 291 33 was originally isolated from symbiotic association with the cycad Macroxamia sp. (Rippka e t al., 1979) and, via infection by hormogonia, can reconstitute a symbiotic (Campbell & Meeks, 1989;Enderlin & Meeks, 1983) and the angiosperm Gztnnera manicata (Johansson & Bergman, 1994 …”