Elastic and Inelastic Light Scattering from Single Bacterial Spores in an Optical Trap Allows the Monitoring of Spore Germination Dynamics

摘要

Raman scattering spectroscopy and elastic light scattering intensity (ESLI) were used to simultaneously measure levels of Ca-dipicolinic acid (CaDPA) and changes in spore morphology and refractive index during germination of individual Bacillus subtilis spores with and without the two redundant enzymes (CLEs), CwlJ and SleB, that degrade spores' peptidoglycan cortexes. Conclusions from these measurements include (1) CaDPA release from individual wild-type germinating spores was biphasic; in a first heterogeneous slow phase, T_(lag), CaDPA levels decreased approx15percent, and in the second phase ending at T_(release), remaining CaDPA was released rapidly; (2) in L-alanine germination of wild-type spores and spores lacking SleB (a) the ESLI rose approx2-fold shortly before T_(lag) at T_(1), (b) following T_(lag), the ESLI again rose approx2-fold at T_(2) when CaDPA levels had decreased approx50percent, and (c) the ESLI reached its maximum value at (approx)T_(release) and then decreased; (3) in CaDPA germination of wildtype spores, (a) T_(lag) increased and the first increase in ESLI occurred well before T_(lag), consistent with different pathways for CaDPA and L-alanine germination, (b) at T_(release), the ESLI again reached its maximum value; (4) in L-alanine germination of spores lacking both CLEs and unable to degrade their cortex, the time (DELTA)T_(release) (T_(release) - T_(lag)) for excretion of >=75percent of CaDPA was approx15-fold higher than that for wild-type or sleB spores; and (5) spores lacking only CwlJ exhibited a similar but not identical ESLI pattern during L-alanine germination to that seen with cwlJ sleB spores and the high value for (DELTA)T_(release).