Bacteria of Bacillus species sporulate upon starvation, and the resultant dormant spores germinate when the environment appears likely to allow the resumption of vegetative growth. Normally, the rates of germination of individual spores in populations are very heterogeneous, and the current work has investigated whether spore-to-spore communication enhances the synchronicity of germination. In order to do this work, time-lapse optical images of thousands of individual spores were captured during germination, and an image analysis algorithm was developed to do the following: (i) measure the positions and germination rates of many thousands of individual spores and (ii) compute pairwise correlations of their germination. This analysis showed that an individual spore's germination rate was dependent on its distance from other spores, especially at short distances. Thus, spores that were within a few micrometers exhibited an increased synchronicity in germination, suggesting that there is a mechanism for short-range communication between such spores during germination. However, two molecules known to be germinants that are released during germination, L-alanine and the 1:1 chelate of Ca 2؉ and dipicolinic acid, did not mediate spore-to-spore communication during germination.Bacteria of Bacillus species form spores in order to survive adverse environmental conditions (18, 28). These spores are metabolically dormant and highly resistant to most antibacterial agents. However, the dormant spores continually monitor their environment and can resume vegetative growth once the environment becomes suitable. The first step in a spore's return to growth is germination, which can be initiated by some specific nutrient germinant molecules, including amino acids, nucleosides, and sugars (16,27). A key early step in germination is the release of the spores' large pool (ϳ20% of the dry weight of spores' central region or core) of dipicolinic acid (DPA) that is chelated to divalent metal ions, predominantly Ca 2ϩ (Ca-DPA) (12,25,27). Recent studies with individual spores have shown that once rapid release of Ca-DPA during germination has begun, it is completed in only a few minutes (4,13,22,27,35). However, there are generally long lag times (t lag ) between the time of addition of a nutrient germinant to the initiation of rapid Ca-DPA release for individual spores, and t lag values vary greatly from spore to spore even in genetically identical populations germinating under the same conditions (4, 35). In contrast, the time needed for release of ϳ90% of a spore's Ca-DPA during germination is relatively constant at several minutes.The precise kinetics of spore germination are of great interest to the food and medical products industries, because once spores have germinated they are much easier to kill than the more resistant dormant spores. Unfortunately, the rates of germination of individual spores are extremely heterogeneous due to the variations in t lag (4,11,13,35). Some of the factors that influence t lag values have recently...

Salinity is one of the main adverse environmental factors severely inhibiting rice growth and decreasing grain productivity. Developing rice varieties with salt tolerance (ST) is one of the most economical approaches to cope with salinity stress. In this study, the salt tolerance of 220 rice accessions from rice diversity panel l (RDP1), representing five subpopulations, were evaluated based on 16 ST indices at both seedling and reproductive stages under salt stress. An apparent inconsistency was found for ST between the two stages. Through a gene-based/tightly linked genome-wide association study with 201,332 single nucleotide polymorphisms (SNPs) located within genes and their flanking regions were used, a total of 214 SNPs related to 251 genes, significantly associated with 16 ST-related indices, were detected at both stages. Eighty-two SNPs with low frequency favorable (LFF) alleles in the population were proposed to hold high breeding potential in improving rice ST. Fifty-four rice accessions collectively containing all these LFF alleles were identified as donors of these alleles. Through the integration of meta-quantitative trait locus (QTL) for ST and the response patterns of differential expression genes to salt stress, thirty-eight candidate genes were suggested to be involved in the regulation of rice ST. In total, the present study provides valuable information for further characterizing ST-related genes and for breeding ST varieties across whole developmental stages through marker-assisted selection (MAS).