Melania Geymonat, 28, and her girlfriend Chris, 29, were on the upper deck of a double-decker night bus when they were attacked by a gang after they refused to kiss.
The fifth arrest was announced on Saturday morning.
The Metropolitan Police said a 16-year-old boy had been arrested on suspicion of robbery and aggravated GBH, and is currently in custody.
In a statement on Facebook after the attack, Ms Geymonat wrote: “What upsets me the most is that violence has become a common thing, that sometimes it’s necessary to see a woman bleeding after having been punched to feel some kind of impact…
“We have to endure verbal harassment and chauvinist, misogynistic and homophobic violence because when you stand up for yourself s*** like this happens.”
When asked if the incident would make her less willing to show affection in public, Chris said: “I am not scared about being visibly queer. If anything, you should do it more.”
And she added: “I was and still am angry. It was scary, but this is not a novel situation.”
Police are still appealing for witnesses and information on the incident, which took place on a route N31 bus in Camden at approximately 2.30am on Thursday 30 May.
Detective Superintendent Andy Cox said: “This was a disgusting attack on two women who appear to have been picked out and targeted by a group of youths.
“The suspects have made a number of homophobic comments towards the couple before throwing coins at them. When the women tried to reason with the group, the attack escalated to an assault.
“Lots of people will understandably be outraged by this attack. Our efforts to trace all the suspects involved and bring them in for questioning will be relentless.”
London mayor Sadiq Khan called it “a disgusting, misogynistic attack. Hate crimes against the LGBT+ community will not be tolerated in London.”
Detectives are asking anyone who witnessed the incident or who may have information that could assist the investigation to contact police on 101 or tweet @MetCC and quote CAD737/30May.
Alternatively, anyone with information can call Crimestoppers anonymously on 0800 555 111.