ri ents ▁are ▁available . ▁Ch rom os om al ▁rep lication ▁is ▁int imately ▁tied ▁to ▁the ▁veget ative ▁cell ▁division ▁cycle ▁( W ang ▁and ▁Le vin ▁ 2 0 0 9 ). ▁The ▁total ▁separation ▁of ▁sister ▁cells ▁by ▁cle av age ▁of ▁the ▁cell ▁wall ▁in ▁Bac ill us ▁species ▁may ▁not ▁occur ▁under ▁some ▁circumstances , ▁and ▁the ▁cells ▁may ▁remain ▁linked ▁together ▁through ▁multiple ▁r ounds ▁of ▁binary ▁f ission , ▁forming ▁long ▁ch ains ▁( Br anda ▁et ▁al ., ▁ 2 0 0 1 , ▁Ch ai ▁et ▁al ., ▁ 2 0 1 0 , ▁K ear ns ▁and ▁Los ick , ▁ 2 0 0 5 ). ▁Ros enberg ▁et ▁al . ▁( 2 0 1 2 ) ▁demonstrated ▁trans cription al ▁vari ability ▁among ▁different ▁b acter ial ▁cells ▁during ▁veget ative ▁growth ▁directly ▁related ▁to ▁nut ri ent ▁avail ability , ▁and ▁this ▁may ▁represent ▁an ▁additional ▁strategy ▁to ▁enh ance ▁population ▁robust ness . ▁ ▁Sp or ulation ▁Multiple ▁environmental ▁signals , ▁such ▁as ▁nut ri ent ▁dep riv ation , ▁high ▁min eral ▁composition , ▁neutral ▁p H , ▁temperature , ▁and ▁high ▁cell ▁density ▁can ▁trigger ▁the ▁different iation ▁of ▁veget ative ▁cells ▁into ▁end os por es . ▁The ▁cell ular ▁mass ▁increases ▁associated ▁with ▁the ▁accum ulation ▁of ▁secret ed ▁pe pt ides ▁are ▁sens ed ▁by ▁cell ▁surface ▁re cept ors ▁that ▁promote ▁the ▁sequ ential ▁activation ▁of ▁the ▁master ▁reg ulator ▁Spo A .